GURFEIN, Circuit Judge:

This appeal involving a regulation of the Food and Drug Administration is not here upon a direct review of agency action. It is an appeal from a judgment of the District Court for the Eastern District of New York (Hon. John J. Dooling, Judge) enjoining the appellants, after a hearing, from processing *243hot smoked whitefish except in accordance with time-temperature-salinity (T-T-S) regulations contained in 21 C.F.R. Part 122 (1977).1 The thorough analytical opinion of the District Court is reported at 417 F.Supp. 1364 (Aug. 17, 1976).

The injunction was sought and granted on the ground that smoked whitefish which has been processed in violation of the TT-S regulation is “adulterated.” Food, Drug and Cosmetics Act (“the Act”) §§ 302(a) and 301(k), 21 U.S.C. §§ 332(a), 331(k).2

Appellant Nova Scotia receives frozen or iced whitefish in interstate commerce which it processes by brining, smoking and cooking. The fish are then sold as smoked whitefish.

The regulations cited above require that hot-process smoked fish be heated by a controlled heat process that provides a monitoring system positioned in as many strategic locations in the oven as necessary to assure a continuous temperature through each fish of not less than 180° F. for a minimum of 30 minutes for fish which have been brined to contain 3.5% water phase salt or at 150° F. for a minimum of 30 minutes if the salinity was at 5% water phase. Since each fish must meet these requirements, it is necessary to heat an entire batch of fish to even higher temperatures so that the lowest temperature for any fish will meet the minimum requirements.3

Government inspection of appellants’ plant established without question that the minimum T-T-S requirements were not being met. There is no substantial claim that the plant was processing whitefish under “insanitary conditions” in any other material respect. Appellants, on their part, do not defend on the ground that they were in compliance, but rather that the requirements could not be met if a marketable whitefish was to be produced. They defend upon the grounds that the regulation is invalid (1) because it is beyond the authority delegated by the statute; (2) because the FDA improperly relied upon undisclosed evidence in promulgating the regulation and because it is not supported by the administrative record; and (3) because there was no adequate statement setting forth the basis of the regulation.4 We reject the contention that the regulation is beyond the authority delegated by the statute, but we find serious inadequacies in the procedure followed in the promulgation of the regulation and hold it to be invalid as applied to the appellants herein.

The hazard which the FDA sought to minimize was the outgrowth and toxin formation of Clostridium botulinum Type E spores of the bacteria which sometimes inhabit fish. There had been an occurrence of several cases of botulism traced to consumption of fish frojn inland waters in 1960 and 1963 which stimulated considerable bacteriological research. These bacteria can be present in the soil and water of various regions. They can invade fish in their natural habitat and can be further disseminated in the course of evisceration and preparation of the fish for cooking. A failure to destroy such spores through an adequate brining, thermal, and refrigeration process was found to be dangerous to public health.

*244The Commissioner of Food and Drugs (“Commissioner”), employing informal “notice-and-eomment” procedures under 21 U.S.C. § 371(a), issued a proposal for the control of C. botulinum bacteria Type E in fish. 34 F.R. 17,176 (Oct. 23,1969). For his statutory authority to promulgate the regulations, the Commissioner specifically relied only upon § 342(a)(4) of the Act which provides:

“A food shall be deemed to be adulterated—

“(4) if it has been prepared, packed, or held under insanitary conditions whereby it may have become contaminated with filth, or whereby it may have been rendered injurious to health;”

Similar guidelines for smoking fish had been suggested by the FDA several years earlier, and were generally made known to people in the industry. At that stage, however, they were merely guidelines without substantive effect as law. Responding to the Commissioner’s invitation in the notice of proposed rulemaking, members of the industry, including appellants and the intervenor-appellant, submitted comments on the proposed regulation.

The Commissioner tilreafter issued the final regulations in which he adopted certain suggestions made in the comments, including a suggestion by the National Fisheries Institute, Inc. (“the Institute”), the intervenor herein. 35 F.R. 17,401 (Nov. 13, 1970).5 The original proposal provided that the fish would have to be cooked to a temperature of 180° F. for at least 30 minutes, if the fish have been brined to contain 3.5% water phase salt, with no alternative. In the final regulation, an alternative suggested by the intervenor “that the parameter of 150° F. for 30 minutes and 5% salt in the water phase be established as an alternate procedure to that stated in the proposed regulation for an interim period until specific parameters can be established” was accepted, but as a permanent part of the regulation rather than for an interim period.

The intervenor suggested that “specific parameters” be established. This referred to particular processing parameters for different species of fish on a “species by species” basis. Such “species by species” determination was proposed not only by the intervenor but also by the Bureau of Commercial Fisheries of the Department of the Interior. That Bureau objected to the general application of the T-T-S requirement proposed by the FDA on the ground that application of the regulation to all species of fish being smoked was not commercially feasible, and that the regulation should therefore specify time-temperature-salinity requirements, as developed by research and study, on a species-by-species basis. The Bureau suggested that “wholesomeness considerations could be more practically and adequately realized by reducing processing temperature and using suitable concentrations of nitrite and salt.” The Commissioner took cognizance of the suggestion, but decided, nevertheless, to impose the T-T-S requirement on all species of fish (except chub, which were regulated by 21 C.F.R. 172.177 (1977) [dealing with food additives]).6

He did acknowledge, however, in his “basis and purpose” statement required by the Administrative Procedure Act (“APA”), 5 U.S.C. § 553(c), that “adequate times, temperatures and salt concentrations have not been demonstrated for each individual species of fish presently smoked”. 35 F.R. 17,401 (Nov. 13, 1970). The Commissioner concluded, nevertheless, that “the processing requirements of the proposed regulations are the safest now known to prevent *245the outgrowth and toxin formation of C. botulinum Type E”. He determined that “the conditions of current good manufacturing practice for this industry should be established without further delay.” Id.

The Commissioner did not answer the suggestion by the Bureau of Fisheries that nitrite and salt as additives could, safely lower the high temperature otherwise required, a solution which the FDA had accepted in the case of chub. Nor did the Commissioner respond to the claim of Nova Scotia through its trade association, the Association of Smoked Fish Processors, Inc., Technical Center that “[t]he proposed process requirements suggested by the FDA for hot processed smoked fish are neither commercially feasible nor based on sound scientific evidence obtained with the variety of smoked fish products to be included under this regulation.” (Exhibit D, Tab A).7

Nova Scotia, in fEs own comment, wrote to the Commissioner that “the heating of certain types of fish to high temperatures will completely destroy the product”. It suggested, as an alternative, that “specific processing procedures could be established for each species after adequate work and experimention [sic] has been done — but not before.” (Id.). We have noted above that the response given by the Commissioner was in general terms. He did not specifically aver that the T-T-S requirements as applied to whitefish were, in fact, commercially feasible.

When, after several inspections and warnings, Nova Scotia failed to comply with the regulation, an action by the United States Attorney for injunctive relief was filed on April 7, 1976, six years later, and resulted in the judgment here on appeal. The District Court denied a stay pending appeal, and no application for a stay was made to this court.

I

The argument that the regulation is not supported by statutory authority cannot be dismissed out of hand. See Schilling v. Rogers, 363 U.S. 666, 676-77, 80 S.Ct. 1288, 1295-96, 4 L.Ed.2d 1478 (1960); see Batterton v. Francis, 432 U.S. 416, 97 S.Ct. 2399, 53 L.Ed.2d 448 (1977). The sole statutory authority relied upon is § 342(a)(4), quoted above. As we were instructed in S. E. C. v. Chenery Corp., 318 U.S. 80, 87, 63 S.Ct. 454, 459, 87 L.Ed. 626 (1943) (Chenery I), “[t]he grounds upon which an administrative order must be judged are those upon which the record discloses that its action was based.” Nor is the Commissioner’s expressed reliance solely on § 342(a)(4) a technicality which might be removed by a later and wiser reliance on another subsection. For in this case, as the agency recognized, there is no other section or subsection that can pass as statutory authority for the regulation. The categories of “adulteration” prohibited in Section 342 all refer to food as an “adulterated” product rather than to the process of preparing food, except for subsection (a)(4) which alone deals with the processing of food.

Appellants contend that the prohibition against “insanitary conditions” embraces conditions only in the plant itself, but does not include conditions which merely inhibit the growth of organisms already in the food when it enters the plant iin its raw state. They distinguish between conditions which are insanitary, which they concede to be within the ambit of § 342(a)(4), and conditions of sterilization required to destroy micro-organisms, which they contend are not.

It is true that on a first reading the language of the subsection appears to cover only “insanitary conditions” “whereby it [the food] may have been rendered injurious to health” (emphasis added). And a plausible argument can, indeed, be made that the references are to insanitary conditions in the plant itself, such as the presence of rodents or insects, e. g., United States v. Park, 421 U.S. 658, 95 S.Ct. 1903, 44 L.Ed.2d 489 (1975); United States v. *246Cassaro, Inc., 443 F.2d 153 (1st Cir. 1971); United States v. Hammond Milling Co., 413 F.2d 608 (5th Cir. 1969), cert. denied, 396 U.S. 1002, 90 S.Ct. 552, 24 L.Ed.2d 494 (1970).

Yet, when we are dealing with the public health, the language of the Food, Drug and Cosmetic Act should not be read too restrictively, but rather as “consistent with the Act’s overriding purpose to protect the public health”. United States v. Bacto-Unidisk, 394 U.S. 784, 798, 89 S.Ct. 1410, 1418, 22 L.Ed.2d 726 (1969). As Justice Frankfurter said in United States v. Dotterweich, 320 U.S. 277, 280, 64 S.Ct. 134, 136, 88 L.Ed. 48 (1943):

“The purposes of this legislation thus touch phases of the lives and health of people which, in the circumstances of modern industrialism, are largely beyond self-protectjon. Regard for these purposes should infuse construction of the legislation if it is to be treated as a working instrument of government and not merely as a collection of English words.”8

Thus, a provision concerning “food additives” has been held to include even poisonous substances which have not been “added” by human hands. United States v. Ewig Bros. Co., 502 F.2d 715, 721-24 (7th Cir. 1974) (Stevens, J. now Mr. Justice Stevens), cert. denied, 420 U.S. 945, 95 S.Ct. 1325, 43 L.Ed.2d 423 (1975).

Section 371(a), applicable to rule-making under § 342(a)(4), provides: “The authority to promulgate regulations for the efficient enforcement of this chapter, except as otherwise provided in this section, is vested in the Secretary.” We read this grant as analogous to the provision “make . such rules and regulations as may be necessary to carry out the provisions of this Act,” in which case “the validity of a regulation promulgated thereunder will be sustained so long as it is ‘reasonably related to the purposes of the enabling legislation.’ [citations omitted]” Mourning v. Family Publications Service, Inc., 411 U.S. 356, 369, 93 S.Ct. 1652, 36 L.Ed.2d 318 (1973). When agency rulemaking serves the purposes of the statute, courts should refuse to adopt a narrow construction of the enabling legislation which would undercut the agency’s authority to promulgate such rules. United States v. Midwest Video Corp., 406 U.S. 649, 92 S.Ct. 1860, 32 L.Ed.2d 390 (1972) (upholding FCC’s authority to promulgate “cablecasting” regulation as “reasonably ancillary to the effective performance of the Commission’s various responsibilities for the regulation of television broadcasting”); and United States v. Storer Broadcasting Co., 351 U.S. 192, 203-04, 76 S.Ct. 763, 100 L.Ed.2d 1081 (1956). The court’s role should be one of constructive cooperation with the agency in furtherance of the public interest. International Harvester Co. v. Ruckelhaus, 155 U.S.App.D.C. 411, 443, 478 F.2d 615, 647 (1973). As the Supreme Court has said, “We are, in the absence of compelling evidence that such was Congress’ intention, unwilling to prohibit administrative action imperative for the achievement of an agency’s ultimate purposes.” In re Permian Basin Area Rate Cases, 390 U.S. 747, 780, 88 S.Ct. 1344, 20 L.Ed.2d 312 (1968).

Appellant’s argument, it should be noted, is not that there has been an unlawful delegation of legislative power, Schechter Poultry Corp. v. United States, 295 U.S. 495, 55 S.Ct. 837, 79 L.Ed. 1570 (1935), or even a delegation of “unfettered discretion.” See Amalgamated Meat Cutters & Butcher Workers v. Connally, 337 F.Supp. 737, 757 (D.D.C.1971) (Leventhal, J.). The argument, fairly construed, is that Congress did not mean to go so far as to require sterilization sufficient to kill bacteria that may be in the food itself rather than bacteria which accreted in the factory through the use of insanitary equipment.

*247There are arguments which can indeed be mustered to support such a broad-based attack under 5 U.S.C. § 706.9

First, the Act deals with standards of identity and various categories that can render food harmful to health. Yet, so far as the category of harmful micro-organisms is concerned, there is only a single provision, 21 U.S.C. § 344, which directly deals with “micro-organisms.” That provision is limited to emergency permit controls dealing with any class of food which the Secretary finds, after investigation, “may, by reason of contamination with micro-organisms during the manufacture, processing or packing thereof in any locality, be injurious to health, and that such injurious nature cannot be adequately determined after such articles have entered interstate commerce, [in which event] he then, and in such case only, shall promulgate regulations providing for the issuance ... of permits . .” (Emphasis added.) It may be argued that the failure to mention “microorganisms” in the “adulteration” section of the Act, which includes § 342(a)(4), means that Congress intended to delegate no further authority to control micro-organisms than is expressed in the “emergency” control of Section 344.

On the other hand, as Judge Dooling held, the manner of processing can surely give rise to the survival, with attendant toxic effects on humans, of spores which would not have survived under stricter “sanitary” conditions. In that sense, treating “insanitary conditions” in relation to the hazard, the interpretation of the District Court which described the word “sanitary” as merely “inelegant” is a fair reading, emphasizing that the food does not have to be actually contaminated during processing and packing but simply that “it may have been rendered injurious to health,” § 342(a)(4), by inadequate sanitary conditions of prevention.

The other argument of some force would involve the difference in agency rulemaking procedure which results from treating the regulations in question as supported by § 342(a)(4). The Act was enacted in substantially its present form in 1938, preceding the APA by about eight years. In 1938 Congress, groping for standards for rule-making and the scope of judicial review (as it still is) created a bifurcated structure for rulemaking and, hence, for judicial review.

Congress decided to allow informal rule-making to the FDA generally, § 371(a), but it also provided for formal rulemaking which, upon request, required “a public hearing for the purpose of receiving evidence relevant and material to the issues raised by such objections.” § 371(e). It further provided that in such cases the “order shall be based only on substantial evidence of record at such hearing and shall set forth, as part of the order, detailed findings of fact on which the order is based.”

The formal rulemaking with its concomitant standard of “substantial evidence of record,” see United States v. Florida East Coast Railway Co., 410 U.S. 224, 93 S.Ct. 810, 35 L.Ed.2d 223 (1973), is limited, however, to rulemaking under specific enumerated sections of the Act. Section 342, the “adulteration” section upon which the Commissioner relied for his statutory authority is not one of these. The section dealing with temporary permits for micro-organisms, § 344, is. See § 371(e)(1). Thus, a temporary suspension because of the presence of micro-organisms in food merits a formal procedure while permanent regulation of micro-organisms is achievable by informal “notice-and-comment” procedure. Even though we read the statute § 342(a)(4) broadly in terms of the authority delegated to the agency, we must, nevertheless, view with some strictness the minimal requirements for the informal “notice and comment” procedure that follows as of course — a matter we shall discuss below.

We do not discount the logical arguments in support of a restrictive reading of *248§ 342(a)(4), but we perceive a larger general purpose on the part of Congress in protecting the public health.

We come to this conclusion, aside from the general rules of construction noted above, for several reasons: First, until this enforcement proceeding was begun, no lawyer at the knowledgeable Food and Drug bar ever raised the question of lack of statutory delegation or even hinted at such a question. Second, the body of data gathered by the experts, including those of the Technical Laboratory of the Bureau of Fisheries manifested a concern about the hazards of botulism. Third, analogously, the Meat Inspection Act of 1907 (now codified as amended at 21 U.S.C. § 608), which hardly provided a clearer standard than does the “insanitary conditions” provision in the Food and Drug Act, has regulations under it concerning mandatory temperatures for processing pork muscle tissue to eliminate the hazard of trichonosis. The statute permits the Secretary “to prescribe the rules and regulations of sanitation under which such establishments shall be maintained”. The current regulation, 9 C.F.R. § 318.10 (1977), provides: “All parts of the pork muscle tissue shall be heated to a temperature not lower than 137° F., and the method used shall be one known to insure such a result.” 9 C.F.R. § 318.10(c)(1) (1977). The same regulation was codified as early as 1949 as 9 C.F.R. § 18.10(c)(1) (1949). These regulations have been assumed for years to have been properly promulgated by the Secretary of Agriculture under the statutory authority given to him.

Lastly, a holding that the regulation of smoked fish against the hazards of botulism is invalid for lack of authority would probably invalidate, to the extent that our ruling would be followed, the regulations concerning the purity of raw materials before their entry into the manufacturing process in 21 C.F.R. Part 113 (1977) (inspection of incoming raw materials for microbiological contamination before thermal processing of low-acid foods packed in hermetically sealed containers), in 21 C.F.R. Part 118 (1977) (pasteurization of milk and egg products to destroy Salmonella micro-organisms before use of the products in cacao products and confectionery), and 21 C.F.R. Part 129 (1977) (product water supply for processing and bottling of bottled drinking water must be of a safe, sanitary quality when it enters the process).

The public interest will not permit invalidation simply on the basis of a lack of delegated statutory authority in this case. A gap in public health protection should not be created in the absence of a compelling reading based upon the utter absence of any statutory authority, even read expansively. Here we find no congressional history on the specific issue involved, and hence no impediment to the broader reading based on general purpose.10 We believe, nevertheless, that it would be in the public interest for Congress to consider in the light of existing knowledge, a legislative scheme for administrative regulation of the processing of food where hazard from micro-organisms in food in its natural state may require affirmative procedures of sterilization. This would entail, as well, a decision on the type of rulemaking procedure Congress thinks fit to impose.

II

Appellants contend that there is an inadequate administrative record upon which to predicate judicial review, and that the failure to disclose to- interested persons the factual material upon which the agency was relying vitiates the element of fairness which is essential to any kind of administrative action. Moreover, they argue that the “concise general statement of *249basis and purpose” by the Commissioner was inadequate. 5 U.S.C. § 553.

The question of what is an adequate “record”11 in informal rulemaking has engaged the attention of commentators for several years.12 The extent of the administrative record required for judicial review of informal rulemaking is largely a function of the shope of judicial review. Even when the standard of review is whether the promulgation of the rule was “arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with law,” as specified in 5 U.S.C. § 706(2)(A), judicial review must nevertheless, be based on the “whole record” (id.). Adequate review of a determination requires an adequate record, if the review is to be meaningful. Davis, Administrative Law in the Seventies, supra, at 669-71. What will constitute an adequate record for meaningful review may vary with the nature of the admininistrative action to be reviewed. Friendly, “Some Kind of Hearing," 123 U.Pa.L.Rev. 1267, 1291-92 (1975). Review must be based on the whole record even when the judgment is one of policy, except that findings of fact such as would be required in an adjudicatory proceeding or in a formal “on the record” hearing for rule-making need not be made. Overton Park, supra, 401 U.S. at 416-18, 91 S.Ct. at 823-25 (1971). Though the action was informal, without an evidentiary record, the review must be “thorough, probing, [and] in depth”. Id., 401 U.S. at 415, 91 S.Ct. 814. See Scalia & Goodman, Procedural Aspects of the Consumer Product Safety Act, 20 U.C.L.A.L.Rev. 899, 934-35 (1973).

This raises several questions regarding the informal rulemaking procedure followed here: (1) What record does a reviewing court look to? (2) How much of what the agency relied on should have been disclosed to interested persons? (3) To what extent must the agency respond to criticism that is material?

A

With respect to the content of the administrative “record,” the Supreme Court has told us that in informal rulemaking, “the focal point for judicial review should be the administrative record already in existence, not some new record made initially in the reviewing court.” See Camp v. Pitts, 411 U.S. 138, 142, 93 S.Ct. 1241, 1244, 36 L.Ed.2d 106 (1973).

No contemporaneous record was made or certified.13 When, during the enforcement action, the basis for the regulation was sought through pretrial discovery, the record was created by searching the files of the FDA and the memories of those who participated in the process of rulemaking. This resulted in what became Exhibit D at the trial of the injunction action. Exhibit D consists of (1) Tab A containing the comments received from outside parties during the administrative “notice-and-comment” *250proceeding and (2) Tabs B through L consisting of scientific data and the like upon which the Commissioner now says he relied but which were not made known to the interested parties.

Appellants object to the exclusion of evidence in the. District Court “aimed directly at showing that the scientific evidence relied upon by the FDA was inaccurate and not based upon a realistic appraisal of the true facts. Appellants attempted to introduce scientific evidence to demonstrate that in fixing the processing parameters FDA relied upon tests in which ground fish were injected with many millions of botulism [sic] spores and then tested for outgrowth at various processing levels whereas the spore levels in nature are far less and outgrowth would have been prevented by far less stringent processing parameters.” (Br. p. 33). The District Court properly excluded the evidence.

In an enforcement action, we must rely exclusively on the record made before the agency to determine the validity of the regulation. The exception to the exclusivity of that record is that “there may be independent judicial fact-finding when issues that were not before the agency are raised in a proceeding to enforce non-adjudicatory agency action.” Overton Park, supra, 401 U.S. at 415, 91 S.Ct. at 823 (1971). (Emphasis added.)

Though this is an enforcement proceeding and the question is close, we think that the “issues” were fairly before the agency and hence that de novo evidence was properly excluded by Judge Dooling. Camp v. Pitts, supra.14 Our concern is, rather, with the manner in which the agency treated the issues tendered.

B

The key issues were (1) whether, in the light of the rather scant history of botulism in whitefish, that species should have been considered separately rather than included in a general regulation which failed to distinguish species from species; (2) whether the application of the proposed T-T-S requirements to smoked whitefish made the whitefish commercially unsaleable; and (3) whether the agency recognized that prospect, but nevertheless decided that the public health needs should prevail even if that meant commercial death for the whitefish industry. The procedural issues were whether, in the light of these key questions, the agency procedure was inadequate because (i) it failed to disclose to interested parties the scientific data and the methodology upon which it relied; and (ii) because it failed utterly to address itself to the pertinent question of commercial feasibility.

1.

The History of Botulism in Whitefish

The history of botulism occurrence in whitefish, as established in the trial record, which we must assume was available to the FDA in 1970, is as follows. Between 1899 and 1964 there were only eight cases of botulism reported as attributable to hot-smoked whitefish. In all eight instances, vacuum-packed whitefish was involved. All of the eight cases occurred in 1960 and 1963. The industry has abandoned vacuum-packing, and there has not been a single case of botulism associated with commercially prepared whitefish since 1963, though 2,750,000 pounds of whitefish are processed annually. Thus, in the seven-year period from 1964 through 1970, 17.25 million pounds of whitefish have been commercially processed in the United States without a single reported case of botulism. The evi*251dence also disclosed that defendant Nova Scotia has been in business some 56 years, and that there has never been a case of botulism illness from the whitefish processed by it.

2.

The Scientific Data

Interested parties were not informed of the scientific data, or at least of a selection of such data deemed important by the agency, so that comments could be addressed to the data. Appellants argue that unless the scientific data relied upon by the agency are spread upon the public records, criticism of the methodology used or the meaning to be inferred from the data is rendered impossible.

We agree with appellants in this case, for although we recognize that an agency may resort to its own expertise outside the record in an informal rulemaking procedure, we do not believe that when the pertinent research material is readily available and the agency has no special expertise on the precise parameters involved, there is any reason to conceal the scientific data relied upon from the interested parties. As Judge Leventhal said in Portland Cement Ass’n v. Ruckelhaus, 158 U.S.App.D.C. 308, 326, 486 F.2d 375, 393 (1973): “It is not consonant with the purpose of a rulemaking proceeding to promulgate rules on the basis of inadequate data, or on data that [in] critical degree, is known only to the agency.” (Emphasis added.) This is not a case where the agency methodology was based on material supplied by the interested parties themselves. Cf. International Harvester Co. v. Ruckelhaus, 155 U.S.App.D.C. 411, 428, 478 F.2d 615, 632 (1973). Here all the scientific research was collected by the agency, and none of it was disclosed to interested parties as the material upon which the proposed rule would be fashioned.15 Nor was an articulate effort made to connect the scientific requirements to available technology that would make commercial survival possible, though the burden of proof was on the agency. This required it to “bear a burden of adducing a reasoned presentation supporting the reliability of its methodology.” International Harvester, supra, 155 U.S.App.D.C. at 439, 478 F.2d at 643.

Though a reviewing court will not match submission against counter-submission to decide whether the agency was correct in its conclusion on scientific matters (unless that conclusion is arbitrary), it will consider whether the agency has taken account of all “relevant factors and whether there has been a clear error of judgment.” Overton Park, supra, 401 U.S. at 415-16, 91 S.Ct. at 823-24; Appalachian Power Co. v. Environmental Protection Agency, 477 F.2d 495, 507 (4th Cir. 1973). In this circuit we have said that “it is ‘arbitrary or capricious’ for-an agency not to take into account all relevant factors in making its determination.” Hanly v. Mitchell, 460 F.2d 640, 648 (2d Cir.), cert. denied, 409 U.S. 990, 93 S.Ct. 313, 34 L.Ed.2d 256 (1972) (an enforcement action under NEPA).

If the failure to notify interested persons of the scientific research upon which the agency was relying actually prevented the presentation of relevant comment, the agency may be held not to have considered all “the relevant factors.” We can think of no sound reasons for secrecy or reluctance to expose to public view (with an exception for trade secrets or national security) the ingredients of the deliberative process. Cf. Mobil Oil Corp. v. FPC, 157 U.S.App.D.C. 235, 256-58, 483 F.2d 1238, 1259-61 (1973). Indeed, the FDA’s own regulations now specifically require that every notice of proposed rulemaking contain “references to all data and information on which the Commissioner relies for the proposal (copies or a full list of which shall be a part of the administrative file on the mat*252ter . . . ).” 21 C.F.R. § 10.40(b)(1) (1977). And this is, undoubtedly, the trend. See, e. g., National Nutritional Foods v. Weinberger, 512 F.2d 688 (2d Cir.), cert. denied, 423 U.S. 827, 96 S.Ct. 44, 46 L.Ed.2d 44 (1975).16

We think that the scientific data should have been disclosed to focus on the proper interpretation of “insanitary conditions.” When the basis for a proposed rule is a scientific decision, the scientific material which is believed to support the rule should be exposed to the view of interested parties for their comment. One cannot ask for comment on a scientific paper without allowing the participants to read the paper. Scientific research is sometimes rejected for diverse inadequacies of methodology; and statistical results are sometimes rebutted because of a lack of adequate gathering technique or of supportable extrapolation. Such is the stuff of scientific debate. To suppress meaningful comment by failure to disclose the basic data relied upon is akin to rejecting comment altogether. For unless there is common ground, the comments are unlikely to be of a quality that might impress a careful agency. The inadequacy of comment in turn leads in the direction of arbitrary decision-making. We do not speak of findings of fact, for such are not technically required in the informal rulemaking procedures. We speak rather of what the agency should make known so as to elicit comments that probe the fundamentals. Informal rule-making does not lend itself to a rigid pattern. Especially, in the circumstance of our broad reading of statutory authority in support of the agency, we conclude that the failure to disclose to interested persons the scientific data upon which the FDA relied was procedurally erroneous. Moreover, the burden was upon the agency to articulate rationally why the rule should apply to a large and diverse class, with the same TT-S parameters made applicable to all species. Cf. Associated Industries of N.Y.S., Inc. v. U.S. Dept. of Labor, 487 F.2d 342, 352-53 (2d Cir. 1973). And cf. Industrial Union Dept. AFL-CIO v. Hodgson, 162 U.S. App.D.C. 331, 499 F.2d 467 (1974).

C

Appellants additionally attack the “concise general statement” required by APA, 5 U.S.C. § 553, as inadequate. We think that, in the circumstances, it was less than adequate. It is not in keeping with the rational process to leave vital questions, raised by comments which are of cogent materiality, completely unanswered. The agencies certainly have a good deal of discretion in expressing the basis of a rule, but the agencies do not have quite the prerogative of obscurantism reserved to legislatures. “Congress did not purport to transfer its legislative power to the unbounded discretion of the regulatory body.” F.C.C. v. RCA Communications, Inc., 346 U.S. 86, 90, 73 S.Ct. 998, 1002, 97 L.Ed. 1470 (1953) (Frankfurter, J.). As was said in Environmental Defense Fund, Inc. v. EPA, 150 U.S.App.D.C. 348, 371, 465 F.2d 528, 540-51 (1972): “We cannot discharge our role adequately unless we hold EPA to a high standard of articulation. Kennecott Copper Corp. v. EPA, ... 149 U.S.App.D.C. 231, 462 F.2d 846 (1972).”

The test of adequacy of the “concise general statement” was expressed by Judge McGowan in the following terms:

“We do not expect the agency to discuss every item of fact or opinion included in the submissions made to it in informal rulemaking. We do expect that, if the judicial review which Congress has thought it important to provide is to be meaningful, the ‘concise general statement of basis and purpose’ mandated by Section 4 will enable us to see what major issues of policy were ventilated by the informal proceedings and why the agency reacted to them as it did.” Automotive Parts & Accessories Ass’n v. Boyd, 132 U.S.App.D.C. 200, 208, 407 F.2d 330, 338 (1968).

And Judge Friendly has noted that “[i]n a case where a proposed standard under *253OSHA [Occupational Safety and Health Act] has been opposed on grounds as substantial as those presented here, the Department has the burden of offering some reasoned explanation.” Associated Industries of New York State, Inc. v. U.S. Department of Labor, supra, 487 F.2d at 352 (emphasis in original).

The Secretary was squarely faced with the question whether it was necessary to formulate a rule with specific parameters that applied to all species of fish, and particularly whether lower temperatures with the addition of nitrite and salt would not be sufficient. Though this alternative was suggested by an agency of the federal government, its suggestion, though acknowledged, was never answered.

Moreover, the comment that to apply the proposed T-T-S requirements to whitefish would destroy the commercial product was neither discussed nor answered. We think that to sanction silence in the face of such vital questions would be to make the statutory requirement of a “concise general statement” less than an adequate safeguard against arbitrary decision-making.

We cannot improve on the statement of the District of Columbia Circuit in Industrial Union Dep’t, AFL-CIO v. Hodgson, 162 U.S.App.D.C. 331, 339, 499 F.2d 467, 475 (1974).17

“What we are entitled to at all events is a careful identification by the Secretary, when his proposed standards are challenged, of the reasons why he chooses to follow one course rather than another. Where that choice purports to be based on the existence of certain determinable facts, the Secretary must, in form as well as in substance, find those facts from evidence in the record. By the same token, when the Secretary is obliged to make policy judgments where no factual certainties exist or where facts alone do not provide the answer, he should so state and go on to identify the considerations he found to be persuasive.”

One may recognize that even commercial infeasibility cannot stand in the way of an overwhelming .public interest. Yet the administrative process should disclose, at least, whether the proposed regulation is considered to be commercially feasible, or whether other considerations prevail even if commercial infeasibility is acknowledged. This kind of forthright disclosure and basic statement was lacking in the formulation of the T-T-S standard made applicable to whitefish. It is easy enough for an administrator to ban everything. In the regulation of food processing, the worldwide need for food also must be taken into account in formulating measures taken for the protection of health. In the light of the history of smoked whitefish to which we have referred, we find no articulate balancing here sufficient to make the procedure followed less than arbitrary.

After seven years of relative inaction, the FDA has apparently not reviewed the TT-S regulations in the light of present scientific knowledge and experience. In the absence of a new- statutory directive by Congress regarding control of micro-organisms, which we hope will be worthy of its consideration, we think that the T-T-S standards should be reviewed again by the FDA.

We cannot, on this appeal, remand to the agency to allow further comments by interested . parties, addressed to the scientific data now disclosed a.t the trial below. We hold in this enforcement proceeding, therefore, that the regulation, as it affects non-vacuum-packed hot-smoked whitefish, was promulgated in an arbitrary manner and is invalid.

When the District Court held the regulation to be valid, it properly exercised its discretion to grant the injunction. In view of our conclusion to the contrary, we must reverse the grant of - the injunction and direct that the complaint be dismissed.

SPROUSE, Circuit Judge:

Chocolate Manufacturers Association (CMA) appeals from the decision of the district court denying it relief from a rule promulgated by the Food and Nutrition Service (FNS) of the United States Depart-*1100merit of Agriculture (USDA or Department). CMA protests that part of the rule that prohibits the use of chocolate flavored milk1 in the federally funded Special Supplemental Food Program for Women, Infants and Children (WIC Program).2 Holding that the Department’s proposed rule-making did not provide adequate notice that the elimination of flavored milk would be considered in the rulemaking procedure, we reverse.

I

Since 1946 USDA has administered a variety of child nutrition programs under the National School Lunch Act3 and the Child Nutrition Act of 1966.4 Besides the WIC Program, these programs are the National School Lunch Program,5 the Special Milk Program for Children,6 the School Breakfast Program,7 the Summer Food Service Program,8 and the Child Care Food Program.9

The WIC Program was established by Congress in 1972 to assist pregnant, postpartum, and breastfeeding women, infants and young children from families with inadequate income whose physical and mental health is in danger because of inadequate nutrition or health care.10 Under the program, the Department designs food packages reflecting the different nutritional needs of women, infants, and children and provides cash grants to state or local agen-ices, which distribute cash or vouchers to qualifying individuals in accordance with Departmental regulations as to the type and quantity of food.

In 1975 Congress revised and extended the WIC Program through fiscal year 197811 and, for the first time, defined the “supplemental foods” which the program was established to provide. The term

shall mean those foods containing nutrients known to be lacking in the diets of populations at nutritional risk and, in particular, those foods and food products containing high-quality protein, iron, calcium, vitamin A, and vitamin C____ The contents of the food package shall be made available in such a manner as to provide flexibility, taking into account medical and nutritional objectives and cultural eating patterns.

Pub.L. No. 94-105, § 17(g)(3), 89 Stat. 511, 520 (1975) (codified at 42 U.S.C. § 1786(g)(3) (1976)) (replaced by 42 U.S.C. § 1786(b)(14) (1982)).

Pursuant to this statutory definition, the Department promulgated new regulations specifying the contents of WIC Program food packages. These regulations specified that flavored milk was an acceptable substitute for fluid whole milk in the food packages for women and children, but not infants.12 This regulation formalized the Department’s practice of permitting the substitution of flavored milk, a practice observed in the WIC Program since its inception in 1973 as well as in several of the other food programs administered by the Department.

In 1978 Congress, in extending the WIC Program through fiscal year 1982, redefined the term “supplemental foods” to mean

those foods containing nutrients determined by nutritional research to be lack*1101ing in the diets of pregnant, breastfeeding, and postpartum women, infants, and children, as prescribed by the Secretary. State agencies may, with the approval of the Secretary, substitute different foods providing the nutritional equivalent of foods prescribed by the Secretary, to allow for different cultural eating patterns.

Pub.L.' No. 95-627, § 17(b)(14), 92 Stat. 3603, 3613 (1978) (codified at 42 U.S.C. § 1786(b)(14) (1982)). Congress stated further:

The Secretary shall prescribe by regulation supplemental foods to be made available in the program under this section. To the degree possible, the Secretary shall assure that the fat, sugar, and salt content of the prescribed foods is appropriate.

Id. at § 17(f)(12), 92 Stat. at 3616 (codified at 42 U.S.C. § 1786(f)(12) (1982)). To comply with this statutory redefinition, the Department moved to redraft its regulations specifying the WIC Program food packages. In doing so it relied upon information collected during an extensive investigative effort which had begun in 1977. In June 1977 the Department held public hearings in seven cities and elicited testimony on the structure and administration of the WIC Program. The Department invited many interested and informed parties to attend these hearings — the governor and chief health officer of every state, the House Education and Labor Committee, the Senate Select Committee on Nutrition Evaluation, state WIC coordinators, industry representatives, and professional and advocacy groups. In addition to information gathered at the public hearings, the Department received periodic reports from the National Advisory Council on Maternal, Infant, and Fetal Nutrition, as well as recommendations from a Food Package Advisory Panel convened in October 1978.

Using this information as well as its own research as a basis, the Department in November 1979 published for comment the proposed rule at issue in this case. 44 Fed.Reg. 69254 (1979). Along with the proposed rule, the Department published a preamble discussing the general purpose of the rule and acknowledging the congressional directive that the Department design food packages containing the requisite nutritional value and appropriate levels of fat, sugar, and salt. Id. at 69254. Discussing the issue of sugar at length, it noted, for example, that continued inclusion of high sugar cereals may be “contrary to nutrition education principles and may lead to unsound eating practices.” Id. at 69263. It also noted that high sugar foods are more expensive than foods with lower sugar content, and that allowing them would be “inconsistent with the goal of teaching participants economical food buying patterns.” Id.

The rule proposed a maximum sugar content specifically for authorized cereals. The preamble also contained a discussion of the sugar content in juice, but the Department did not propose to reduce the allowable amount of sugar in juice because of technical problems involved in any reduction. Neither the rule nor the preamble discussed sugar in relation to flavoring in milk. Under the proposed rule, the food packages for women and children without special dietary needs included milk that could be “flavored or unflavored.” Id.

The notice allowed sixty days for comment and specifically invited comment on the entire scope of the proposed rules: “The public is invited to submit written comments in favor of or in objection to the proposed regulations or to make recommendations for alternatives not considered in the proposed regulations.” Id. at 69255. Over 1,000 comments were received from state and local agencies, congressional offices, interest groups, and WIC Program participants and others. Seventy-eight commenters, mostly local WIC administrators, recommended that the agency delete flavored milk from the list of approved supplemental foods.

In promulgating the final rule, the Department, responding to these public comments, deleted flavored milk from the list, explaining:

*1102In the previous regulations, women and children were allowed to receive flavored or unflavored milk. No change in this provision was proposed by the Department. However, 78 eommenters requested the deletion of flavored milk from the food packages since flavored milk has a higher sugar content than unflavored milk. They indicated that providing flavored milk contradicts nutrition education and the Department’s proposal to limit sugar in the food packages. Furthermore, flavored milk is more expensive than unflavored milk. The Department agrees with these concerns. There are significant differences in the sugar content of fluid whole milk and low fat chocolate milk. Fluid whole milk supplies 12.0 grams of carbohydrate per cup compared to 27.3 grams of carbohydrate per cup provided by low fat chocolate milk. If we assume that the major portion of carbohydrate in milk is in the form of simple sugar, fluid whole milk contains 4.9% sugar contrasted with 10.9% sugar in low fat chocolate milk. Therefore, to reinforce nutrition education, for consistency with the Department’s philosophy about sugar in the food packages, and to maintain food package costs at economic levels, the Department is deleting flavored milk from the food packages for women and children. Although the deletion of flavored milk was not proposed, the comments and the Department’s policy on sugar validate this change.

45 Fed.Reg. 74854, 74865-66 (1980).

After the final rule was issued, CMA petitioned the Department to reopen the-rulemaking to allow it to comment, maintaining that it had been misled into believing that the deletion of flavored milk would not be considered. In a letter to CMA dated November 18, 1981, the Department indicated that it would reopen the issue of flavored milk for “further public comments” and would request “rationale both supporting and opposing the disallowance of flavored milk in the WIC Program.” It subsequently reversed this position, however, and declined to reopen the rulemak-ing procedure.

On this appeal, CMA contends first that the Department did not provide notice that the disallowance of flavored milk would be considered, and second that the Department gave no reasoned justification for changing its position about the nutritional value of chocolate in the food distributed under its authority. The Department responds to the first contention by arguing that its notice advised the public of its general concern about high sugar content in the proposed food packages and that this should have alerted potentially interested eommenters that it would consider eliminating any food with high sugar content. It also argues in effect that the inclusion of flavored milk in the proposed rule carried with it the implication that both inclusion and exclusion would be considered in the rulemaking process. Because we agree with CMA that the Department provided inadequate notice and, therefore, that it must reopen the comment period on the rule, we do not reach the issue of the reasonable justification for its change of position.

II

The requirement of notice and a fair opportunity to be heard is basic to administrative law. See 1 K. Davis, Administrative Law Treatise § 6.1 at 450 (2d ed. 1978). Our single chore is to determine if the Department’s notice provided interested persons, including CMA, with that opportunity. We must decide whether inclusion of flavored milk in the allowable food packages under the proposed rule should have alerted interested persons that the Department might reverse its position and exclude flavored milk if adverse comments recommended its deletion from the program.

Section 4 of the Administrative Procedure Act (APA) requires that the notice in the Federal Register of a proposed rulemaking contain “either the terms or substance of the proposed rule or a description of the subjects and issues involved.” 5 *1103U.S.C. § 553(b)(3) (1982). The purpose of the notice-and-comment procedure is both “to allow the agency to benefit from the experience and input of the parties who file comments ... and to see to it that the agency maintains a flexible and open-minded attitude towards its own rules.” National Tour Brokers Ass’n v. United States, 591 F.2d 896, 902 (D.C.Cir.1978). The notice-and-comment procedure encourages public participation in the administrative process and educates the agency, thereby helping to ensure informed agency decisionmaking. Spartan Radiocasting Co. v. FCC, 619 F.2d 314, 321 (4th Cir. 1980); BASF Wyandotte Corp. v. Costle, 598 F.2d 637, 642 (1st Cir.1979), cert. denied, 444 U.S. 1096, 100 S.Ct. 1063, 62 L.Ed.2d 784 (1980).

The Department’s published notice here consisted of the proposed rule and a preamble discussing the negative effect of high sugar content in general and specifically in relation to some foods such as cereals and juices, but it did not mention high sugar content in flavored milk. The proposed rule eliminated certain foods with high sugar content but specifically authorized flavored milk as part of the permissible diet. In a discussion characterized by pointed identification of foods with high sugar content, flavored milk was conspicious by its exclusion. If after comments the agency had adopted without change the proposed rule as its final rule, there could have been no possible objection to the adequacy of notice. The public was fully notified as to what the Department considered to be a healthy and adequate diet for its target group. The final rule, however, dramatically altered the proposed rule, changing for the first time the milk content of the diet by deleting flavored milk. The agency concedes that the elimination of flavored milk by the final rule is a complete reversal from its treatment in the proposed rule, but it explains that the reversal was caused by the comments received from 78 interested parties — primarily professional administrators of the WIC Program.

This presents then not the simple question of whether the notice of a proposed rule adequately informs the public of its intent, but rather the question of how to judge the adequacy of the notice when the proposal it describes is replaced by a final rule which reaches a conclusion exactly opposite to that proposed, on the basis of comments received from parties representing only a single view of a controversy.13 In reviewing the propriety of such agency action, we are not constrained by the same degree of deference we afford most agency determinations. “Though our review of an agency’s final decision is relatively narrow, we must be strict in reviewing an agency’s compliance with procedural rules.” BASF Wyandotte Corp. v. Costle, 598 F.2d at 641; see also Weyerhauser Co. v. Costle, 590 F.2d 1011, 1025-28 (D.C.Cir.1978) (whereas a court defers to an agency’s technical judgments, it is less hesitant to reject the agency’s interpretation of statutes, and in reviewing an agency’s procedural integrity, the court relies on its own independent judgment). “The question of adequacy of notice where a proposed rule is changed after comment ... requires careful consideration on a case-by-case basis.” BASF, 598 F.2d at 642.

There is no question that an agency may promulgate a final rule that differs *1104in some particulars from its proposal. Otherwise the agency “can learn from the comments on its proposals only at the peril of starting a new procedural round of commentary.” International Harvester Co. v. Ruckelshaus, 478 F.2d 615, 632 n. 51 (D.C. Cir.1973). An agency, however, does not have carte blanche to establish a rule contrary to its original proposal simply because it receives suggestions to alter it during the comment period. An interested party must have been alerted by the notice to the possibility of the changes eventually adopted from the comments. Wagner Electric Corporation v. Volpe, 466 F.2d 1013, 1019 (3rd Cir.1972). Although an agency, in its notice of proposed rulemaking, need not identify precisely every potential regulatory change, Spartan Radio-casting Co., 619 F.2d at 321-22 (quoting Consolidation. Coal Co. v. Costle, 604 F.2d 239, 248 (4th Cir.1979), rev’d on other grounds sub nom. EPA v. National Crushed Stone Ass’n, 449 U.S. 64, 101 S.Ct. 295, 66 L.Ed.2d 268 (1980), the notice must be sufficiently descriptive to provide interested parties with a fair opportunity to comment and to participate in the rulemaking. United States v. Allegheny-Ludlum Steel Corp., 406 U.S. 742, 758, 92 S.Ct. 1941, 1951, 32 L.Ed.2d 453 (1972); Portland Cement Ass’n v. Ruckelshaus, 486 F.2d 375, 392-94 (D.C.Cir.1973), cert. denied, 417 U.S. 921, 94 S.Ct. 2628, 41 L.Ed.2d 226 (1974).

As we have indicated, appellate review of changes in a proposed rule after comments is more specifically controlled by the circumstances of each case than most administrative appeals. Nevertheless, a review of decisions of our sister circuits performing similar tasks is helpful. In BASF Wyandotte Corp. v. Costle, 598 F.2d 637 (1st Cir.1979), cert. denied, 444 U.S. 1096, 100 S.Ct. 1063, 62 L.Ed.2d 784 (1980), the court considered an EPA regulation controlling the discharge of pollutants into navigable waters by the pesticide industry. The EPA originally proposed dividing the organic pesticide industry into three subcategories, setting different pollutant standards for each one. The industry, arguing for expansion of the number of subcategories and, therefore, pollutant standards, submitted comments demonstrating that the proposed three subcategories were indistinguishable. The EPA, while agreeing with the comments, chose a different solution: it altered its initial rule by eliminating the subcategories and applying uniform standards throughout the entire organic pesticide industry. The industry complained that the EPA’s decision to contract rather than expand the number of subcategories took them entirely by surprise. “The essential inquiry,” the court said, “is whether the commentators have had a fair opportunity to present their views on the contents of the final plan.” Id. at 642. The First Circuit reasoned that even if the initial rule had proposed uniform standards, the content of petitioner’s comments would not have been different for they still would have argued, albeit more voluminously and vociferously, for more subcategories. Id. at 644. The petitioners, therefore, “had a fair opportunity to present their views.” Id.

In International Harvester Co. v. Ruck-elshaus, 478 F.2d 615 (D.C.Cir.1973), the court considered an EPA decision to deny applications by vehicle manufacturers for a one-year suspension of the emission standards for light-duty vehicles. The court upheld the agency’s denial even though the petitioners were precluded from commenting on the methodology that the EPA had used to determine that compliance with the emission standards was technologically possible. The court based this holding on tlje fact that the methodology in question was developed in part on the basis of the petitioners’ submissions at prior hearings. The court stated that “[t]he requirement of submission of a proposed rule for comment does not automatically generate a new opportunity for comment merely because the rule promulgated by the agency differs from the rule it proposed, partly at least in response to submissions.” Id. at 632 (footnote omitted).

In South Terminal Corp. v. EPA, 504 F.2d 646 (1st Cir.1974), the court con*1105sidered an air quality transportation control plan for Boston, Massachusetts, which varied substantially from the proposal described in the notice. The petitioners contended that they had no meaningful notice of the substance of the plan. The South Terminal court identified two factors of primary importance in determining whether a substantially revised final rule is promulgated in accordance with the APA: the changes in the original rule must be “in character with the original scheme” and “a logical outgrowth” of the notice and comment already given. Id. at 658, 659; see also BASF Wyandotte Corp. v. Costle, 598 F.2d at 642. In rejecting the petitioners’ claim, the court stated: “Although the changes were substantial, they were in character with the original scheme and were additionally foreshadowed in proposals and comments advanced during the rulemaking. [In addition, the parties] had been warned that strategies might be modified in light of their suggestions.” 504 F.2d at 658. A proposed rule, therefore, must fairly apprise interested parties of the potential scope and substance of a substantially revised final rule and, under this approach, a substantial change must relate in part to the comments received.

While considering factors similar to those applied in the above cases, the Third Circuit, in Wagner Electric Corporation v. Volpe, 466 F.2d 1013 (3rd Cir.1972), found notice inadequate where a final rule had been substantially altered from the one described in the initial notice. The National Highway Traffic Safety Administration had published a proposed rule governing hazard warning flashers. The proposed rule would have eliminated the permissible failure rate for flashers, but it said nothing about changing the pertinent performance criteria. The final rule substantially downgraded the performance criteria for flashers. Despite the fact that several comments by manufacturers suggested downgrading the performance criteria, the court concluded that the agency’s proposed rule provided inadequate notice of its final rule because it failed to apprise all interested parties of the issue of performance criteria. Id. at 1019-20. In support of this conclusion, the court noted the absence of comments from groups which could be expected to oppose downgrading the performance criteria, for example, consumer groups and state highway agencies. Id.

The test devised by the First Circuit for determining adequacy of notice of a change in a proposed rule occurring after comments appears to us to be sound: notice is adequate if the changes in the original plan “are in character with the original scheme,” and the final rule is a “logical outgrowth” of the notice and comments already given. See, e.g., BASF Wyandotte Corp. v. Costle, 598 F.2d 637, 642 (1st Cir.1979), cert. denied, 444 U.S. 1096, 100 S.Ct. 1063, 62 L.Ed.2d 784 (1980); South Terminal Corp. v. EPA, 504 F.2d 646, 659 (1st Cir.1974). Other circuits also have adopted some form of the “logical outgrowth” . test. See, e.g., Sierra Club v. Costle, 657 F.2d 298, 352 (D.C.Cir.1981) (logical outgrowth of the notice and comments); Taylor Diving & Salvage Co. v. Dept. of Labor, 599 F.2d 622, 626 (5th Cir.1979) (logical outgrowth of the standard originally proposed). Stated differently, if the final rule materially alters the issues involved in the rulemaking or, as stated in Rowell v. Andrus, 631 F.2d 699, 702 n. 2 (10th Cir.1980), if the final rule “substantially departs from the terms or substance of the proposed rule,” the notice is inadequate.

There can be no doubt that the final rule in the instant case was the “outgrowth” of the original rule proposed by the agency, but the question of whether the change in it was in character with the original scheme and whether it was a “logical outgrowth” is not easy to answer. In resolving this difficult issue, we recognize that, although helpful, verbal formulations are not omnipotent talismans, and we agree that in the final analysis each case “must turn on how well the notice that the agency gave serves the policies underlying the notice requirement.” Small Refiner Lead Phase-Down Task Force v. EPA, 705 F.2d 506, 547 (D.C.Cir.1983). Under either view, we do *1106not feel that CMA was fairly treated or that the administrative rulemaking process was well served by the drastic alteration of the rule without an opportunity for CMA to be heard.

It is apparent that for many years the Department of Agriculture has permitted the use of chocolate in some form in the food distribution programs that it administers. The only time the Department has proposed to remove chocolate in any form from its programs was in April 1978 when it sought to characterize chocolate as a candy and remove it from the School Lunch Program. That proposal was withdrawn after CMA commented, supporting chocolate as a part of the diet. Chocolate flavored milk has been a permissible part of the WIC Program diet since its inception and there have been no proposals for its removal until the present controversy.

The Department sponsored commendable information-gathering proceedings prior to publishing its proposed rule. Together with its own research, the information gathered in the pre-publication information solicitations formed the basis for the proposed rule. Most of the same information was presented to Congress prior to enactment of the 1978 statute that precipitated the 1979 rulemaking here in controversy. The National Advisory Council on Maternal, Infant, and Fetal Nutrition provided information and advice. Regional council meetings were open to the public and held in diverse areas of the country. Department of Agriculture personnel attended a number of regional, state, and local meetings and gathered opinions concerning possible changes in the food packages. The agency also gathered a food package advisory panel of experts seeking their recommendations. Food packages were designed based on the information and advice gleaned from these sources. In all of these activities setting out and discussing food packages, including the proposed rule and its preamble, the Department never suggested that flavored milk be removed from the WIC Program.

The published preamble to the proposed rule consisted of twelve pages in the Federal Register discussing in detail factors that would be considered in making the final rule. Two pages were devoted to a general discussion of nutrients, including protein, iron, calcium, vitamin A, vitamin C, folic acid, zinc, and fiber, and the dangers of overconsumption of sugar, fat, and salt. The preamble discussed some foods containing these ingredients and foods posing specific problems. It did not discuss flavored milk.

In the next eight pages of the preamble, the nutrition content of food packages was discussed — under the general headings of “cereal” and “juice” for infants; and “eggs,” “milk,” “cheese,” “peanut butter and mature dried beans and peas,” “juice,” “additional foods,” “cereals,” “iron,” “sugar,” “whole grain cereals,” “highly fortified cereals,” and “artificial flavors and colors” for women and children. The only reference to milk concerned the correct quantity to be provided to children, i.e., 24 quarts per month instead of 28 quarts. Although there was considerable discussion of the sugar content of juice and cereal, there was none concerning flavored milk. Likewise, there was considerable discussion of artificial flavor and color in cereal but none concerning flavored milk. The only reference to flavored milk was in the two-page discussion of the individual food packages, which noted that the proposed rule would permit the milk to be flavored or unflavored. The proposed rule which followed the preamble expressly noted that flavored or unflavored milk was permitted in the individual food packages for women and children without special dietary needs.

At the time the proposed rulemaking was published, neither CMA nor the public in general could have had any indication from the history of either the WIC Program or any other food distribution programs that flavored milk was not part of the acceptable diet for women and children without special dietary needs. The discus*1107sion in the preamble to the proposed rule was very detailed and identified specific foods which the agency was examining for excess sugar. This specificity, together with total silence concerning any suggestion of eliminating flavored milk, strongly indicated that flavored milk was not at issue. The proposed rule positively and unqualifiedly approved the continued use of flavored milk. Under the specific circumstances of this case, it cannot be said that the ultimate changes in the proposed rule were in character with the original scheme or a logical outgrowth of the notice. We can well accept that, in general, an approval of a practice in a proposed rule may properly alert interested parties that the practice may be disapproved in the final rule in the event of adverse comments. The total effect of the history of the use of flavored milk, the preamble discussion, and the proposed rule, however, could have led interested persons only to conclude that a change in flavored milk would not be considered. Although ultimately their comments may well have been futile, CMA and other interested persons at least should have had the opportunity to make them. We believe that there was insufficient notice that the deletion of flavored milk from the WIC Program would .be considered if adverse comments were received and, therefore, that affected parties did not receive a fair opportunity to contribute to the administrative rulemaking process. That process was ill-served by the misleading or inadequate notice concerning the permissibility of chocolate flavored milk in the WIC Program and “does not serve the policy underlying the notice requirement.”

The judgment of the district court is therefore reversed, and the case is remanded to the administrative agency with instructions to reopen the comment period and thereby afford interested parties a fair opportunity to comment on the proposed changes in the rule.

REVERSED AND REMANDED WITH INSTRUCTIONS.

*523Mr. Justice Rehnquist

delivered the opinion of the Court.

In 1946, Congress enacted the Administrative Procedure Act, which as we have noted elsewhere was not only “a new, basic and comprehensive regulation of procedures in many agencies,” Wong Yang Sung v. McGrath, 339 U. S. 33 (1950), but was also a legislative enactment which settled “long-continued and hard-fought contentions, and enacts a formula upon which opposing social and political forces have come to rest.” Id., at 40. Section 4 of the Act, 5 U. S. C. § 553 (1976 ed.), dealing with rulemaking, requires in subsection (b) that *524“notice of proposed rule making shall be published in the Federal Register . . . describes the contents of that notice, and goes on to require in subsection (c) that after the notice the agency “shall give interested persons an opportunity to participate in the rule making through submission of written data, views, or arguments with or without opportunity for oral presentation. After consideration of the relevant matter presented, the agency shall incorporate in the rules adopted a concise general statement of their basis and purpose.” Interpreting this provision of the Act in United States v. AlleghenyLudlum Steel Corp., 406 U. S. 742 (1972), and United States v. Florida East Coast R. Co., 410 U. S. 224 (1973), we held that generally speaking this section of the Act established the maximum procedural requirements which Congress was willing to have the courts impose upon agencies in conducting rulemaking procedures.1 Agencies are free to grant additional procedural rights in the exercise of their discretion, but reviewing courts are generally not free to impose them if the agencies have not chosen to grant them. This is not to say necessarily that there are no circumstances- which would ever justify a court in overturning agency action because of a failure to employ procedures beyond those required by the statute. But such circumstances, if they exist, are extremely rare.

Even apart from the Administrative Procedure Act this Court has for more than four decades emphasized that the formulation of procedures was basically to be left within the discretion of the agencies to which Congress had confided the responsibility for substantive judgments. In FCC v. Schreiber, 381 U. S. 279, 290 (1965), the Court explicated *525this principle, describing it as “an outgrowth of the congressional determination that administrative agencies and administrators will be familiar with the industries which they regulate and will be in a better position than federal courts or Congress itself to design procedural rules adapted to the peculiarities of the industry and the tasks of the agency involved.” The Court there relied on its earlier ease of FCC v. Pottsville Broadcasting Co., 309 U. S. 134, 138 (1940), where it had stated that a provision dealing with the conduct of business by the Federal Communications Commission delegated to the Commission the power to resolve “subordinate questions of procedure . . . [such as] the scope of the inquiry, whether applications should be heard contemporaneously or successively, whether parties should be allowed to intervene in one another’s proceedings, and similar questions.”

It is in the light of this background of statutory and decisional law that we granted certiorari to review two judgments of the Court of Appeals for the District of Columbia Circuit because of our concern that they had seriously misread or misapplied this statutory and decisional law cautioning reviewing courts against engrafting their own notions of proper procedures upon agencies entrusted with substantive functions by Congress. 429 U. S. 1090 (1977). We conclude that the Court of Appeals has done just that in these cases, and we therefore remand them to it for further proceedings. We also find it necessary to examine the Court of Appeals’ decision with respect to agency action taken after full adjudicatory hearings. We again conclude that the court improperly intruded into the agency’s decisionmaking process, making it necessary for us to reverse and remand with respect to- this part of the cases also.

I

A

Under the Atomic Energy Act of 1954, 68 Stat. 919, as amended, 42 U. S. C. § 2011 et seq., the Atomic Energy Comm*526ission2 was given broad regulatory authority over the development of nuclear energy. Under the terms of the Act, a utility seeking to construct and operate a nuclear power plant must obtain a separate permit or license at both the construction and the operation stage of the project. See 42 U. S. C. §§ 2133, 2232, 2235, 2239. In order to obtain the construction permit, the utility must file a preliminary safety analysis report, an environmental report, and certain information regarding the antitrust implications of the proposed project. See 10 CFR §§2.101, 50.30 (f), 50.33a, 50.34 (a) (1977). This application then undergoes exhaustive review by the Commission’s staff and by the Advisory Committee on Reactor Safeguards (ACRS), a group of distinguished experts in the field of atomic energy. Both groups submit to the Commission their own evaluations, which then become part of the record of the utility’s application.3 See 42 U. S. C. §§ 2039, 2232 (b). The Commission staff also undertakes the review required by the National Environmental Policy Act of 1969 (NEPA), 83 Stat. 852, 42 U. S. C. §4321 et seq., and prepares a draft environmental impact statement, which, after being circulated for comment, 10 CFR §§ 51.22-51.25 (1977), is revised and becomes a final environmental impact statement. § 51.26. Thereupon a three-member Atomic Safety and Licensing Board conducts a public adjudicatory hearing, 42 U. S. C. § 2241, and reaches a decision4 which can be *527appealed to the Atomic Safety and Licensing Appeal Board, and currently, in the Commission’s discretion, to the Commission itself. 10 CFR §§ 2.714, 2.721, 2.786, 2.787 (1977). The final agency decision may be appealed to the courts of appeals. 42 U. S. C. § 2239; 28 U. S. C. § 2342. The same sort of process occurs when the utility applies for a license to operate the plant, 10 CFR § 50.34 (b) (1977), except that a hearing need only be held in contested cases and may be limited to the matters in controversy. See 42 U. S. C. § 2239 (a); 10 CFR §2.105 (1977); 10 CFR pt. 2, App. A, V (f) (1977).5

These cases arise from two separate decisions of the Court of Appeals for the District of Columbia Circuit. In the first, the court remanded a decision of the Commission to grant a license to petitioner Vermont Yankee Nuclear Power Corp. to operate a nuclear power plant. Natural Resources Defense Council v. NRC, 178 U. S. App. D. C. 336, 547 F. 2d 633 (1976). In the second, the court remanded a decision of that same agency to grant a permit to petitioner Consumers Power Co. to construct two pressurized water nuclear reactors to generate electricity and steam. Aeschliman v. NRC, 178 U. S. App. D. C. 325, 547 F. 2d 622 (1976).

B

In December 1967, after the mandatory adjudicatory hearing and necessary review, the Commission granted petitioner Vermont Yankee a permit to build a nuclear power plant in Vernon, Vt. See 4 A. E. C. 36 (1967). Thereafter, Vermont Yankee applied for an operating license. Respondent Natural Resources Defense Council (NRDC) objected to the granting *528of a license, however, and therefore a hearing on the application commenced on August 10, 1971. Excluded from consideration at the hearings, over NRDC’s objection, was the issue of the environmental effects of operations to reprocess fuel or dispose of wastes resulting from the reprocessing operations.6 This ruling was affirmed by the Appeal Board in June 1972.

In November 1972, however, the Commission, making specific reference to the Appeal Board’s decision with respect to the Vermont Yankee license, instituted rulemaking proceed-' ings “that would specifically deal with the question of consideration of environmental effects associated with the uranium fuel cycle in the individual cost-benefit analyses for light water cooled nuclear power reactors.” App. 352.' The notice of proposed rulemaking offered two alternatives, both predicated on a report prepared by the Commission’s staff entitled Environmental Survey of the Nuclear Euel Cycle. The first would have required no quantitative evaluation of the environmental hazards of fuel reprocessing or disposal because the Environmental Survey had found them to be slight. The second would have specified numerical values for the environmental impact of this part of the fuel cycle, which values would then be incorporated into a table, along with the other relevant factors, to determine the overall cost-benefit balance for each operating license. See id., at 356-357.

Much of the controversy in this case revolves around the *529procedures used in the rulemaking hearing which commenced in February 1973. In a supplemental notice of hearing the Commission indicated that while discovery or cross-examination would not be utilized, the Environmental Survey would be available to the public before the hearing along with the extensive background documents cited therein. All participants would be given a reasonable opportunity to present their position and could be represented by counsel if they so desired. Written and, time permitting, oral statements would be received and incorporated into the record. All persons giving oral statements would be subject to questioning by the Commission. At the conclusion of the hearing, a transcript would be made available to the public and the record would remain open for 30 days to allow the filing of supplemental written statements. See generally id., at 361-363. More than 40 individuals and organizations representing a wide variety of interests submitted written comments. On January 17, 1973, the Licensing Board held a planning session to schedule the appearance of witnesses and to discuss methods for compiling a record. The hearing was held on February 1 and 2, with participation by a number of groups, including the Commission’s staff, the United States Environmental Protection Agency, a manufacturer of reactor equipment, a trade association from the nuclear industry, a group of electric utility companies, and a group called Consolidated National Intervenors which represented 79 groups and individuals including respondent NRDC.

After the hearing, the Commission’s staff filed a supplemental document for the purpose of clarifying and revising the Environmental Survey. Then the Licensing Board forwarded its report to the Commission without rendering any decision. The Licensing Board identified as the principal procedural question the propriety of declining to use full formal adjudicatory procedures. The major substantive issue was the technical adequacy of the Environmental Survey.

*530In April 1974, the Commission issued a rule which adopted the second of the two proposed alternatives described above. The Commission also approved the procedures used at the hearing,7 and indicated that the record, including the Environmental Survey, provided an “adequate data base for the regulation adopted.” Id., at 392. Finally, the Commission ruled that to the extent the rule differed from the Appeal Board decisions in Vermont Yankee “those decisions have no further precedential significance,” id., at 386, but that since “the environmental effects of the uranium fuel cycle have been shown to be relatively insignificant, ... it is unnecessary to apply the amendment to applicant’s environmental reports submitted prior to its effective date or to Final Environmental Statements for which Draft Environmental Statements have been circulated for comment prior to the effective date,” id., at 395.

Respondents appealed from both the Commission’s adoption of the rule and its decision to grant Vermont Yankee’s license to the Court of Appeals for the District of Columbia Circuit.

C

In January 1969, petitioner Consumers Power Co. applied for a permit to construct two nuclear reactors in Midland, *531Mich. Consumers Power’s application was examined by the Commission’s staff and the ACRS. The ACRS issued reports which discussed specific problems and recommended solutions. It also made reference to “other problems” of a more generic nature and suggested that efforts should be made to resolve them with respect to these as well as all other projects.8 Two groups, one called Saginaw and another called Mapleton, intervened and opposed the application.9 Saginaw filed with the Board a number of environmental contentions, directed over 300 interrogatories to the ACRS, attempted to depose the chairman of the ACRS, and requested discovery of various ACRS documents. The Licensing Board denied the various discovery requests directed to the ACRS. Hearings were then held on numerous radiological health and safety issues.10 Thereafter, the Commission’s staff issued a draft *532environmental impact statement. Saginaw submitted 119 environmental contentions which were both comments on the proposed draft statement and a statement of Saginaw’s position in the upcoming hearings. The staff revised the statement and issued a final environmental statement in March 1972. Further hearings were then conducted during May and June 1972. Saginaw, however, choosing not to appear at or participate in these latter hearings, indicated that it had “no conventional findings of fact to set forth” and had not “chosen to search the record and respond to this proceeding by submitting citations of matters which we believe were proved or disproved.” See App. 190 n. 9. But the Licensing Board, recognizing its obligations to “independently consider the final balance among conflicting environmental factors in the record,” nevertheless treated as contested those issues “as to which intervenors introduced affirmative evidence or engaged in substantial cross examination.” Id., at 205, 191.

At issue now are 17 of those 119 contentions which are claimed to raise questions of “energy conservation.”', The Licensing Board indicated that as far as appeared from the record, the demand for the plant was made up, of normal industrial and residential use. Id., at 207. It went on to state that it was “beyond our province to inquire into whether the customary uses being made of electricity in our society are ‘proper’ or ‘improper.’ ” Ibid. With respect to claims that Consumers Power stimulated demand by its advertising the Licensing Board indicated that “[n]o evidence was offered on this point and absent some evidence that Applicant is creating abnormal demand, the Board did not consider the *533question.” Id., at 207-208. The Licensing Board also' failed to consider the environmental effects of fuel reprocessing or disposal of radioactive wastes. The Appeal Board ultimately-affirmed the Licensing Board’s grant of a construction permit and the Commission declined to further review the matter.

At just about the same time, the Council on Environmental Quality revised its regulations governing the preparation of environmental impact statements. 38 Fed. Reg. 20550 (1973). The regulations mentioned for the first time the necessity of considering in impact statements energy conservation as one of the alternatives to a proposed project. The new guidelines were to apply only to final impact statements filed after January 28, 1974. Id., at 20557. Thereafter, on November 6, 1973, more than a year after the record had been closed in the Consumers Power case and while that case was pending before the Court of Appeals, the Commission ruled in another case that while its statutory power to compel conservation was not clear, it did not follow that all evidence of energy conservation issues should therefore be barred at the threshold. In re Niagara Mohawk Power Corp., 6 A. E. C. 995 (1973). Saginaw then moved the Commission to clarify its ruling and reopen the Consumers Power proceedings.

In a lengthy opinion, the Commission declined to reopen the proceedings. The Commission first ruled it was required to consider only energy conservation alternatives which 'were “ ‘reasonably available,’ ” would in their aggregate effect curtail demand for electricity to a level at which the proposed facility would not be needed, and were susceptible of a reasonable degree of proof. App. 332. It then determined, after a thorough examination of the record, that not all of Saginaw’s contentions met these threshold tests. Id., at 334-340. It further determined that the Board had been willing at all times to take evidence on the other contentions. Saginaw had simply failed to present any such evidence. The *534Commission further criticized Saginaw for its total disregard of even those minimal procedural formalities necessary to give the Board some idea of exactly what was at issue. The Commission emphasized that “[particularly in these circumstances, Saginaw’s complaint that it was not granted a hearing on alleged energy conservation issues comes with ill grace.”11 Id., at 342. And in response to Saginaw’s contention that regardless of whether it properly raised the issues, the Licensing Board must consider all environmental issues, the Commission basically agreed, as did the Board itself, but further reasoned that the Board must have some workable procedural rules and these rules

“in this setting must take into account that energy conservation is a novel and evolving concept. NEPA 'does not require a “crystal ball” inquiry.’ Natural Resources Defense Council v. Morton, [148 U. S. App. D. C. 5, 15, 458 F. 2d 827, 837 (1972) ]. This consideration has led us to hold that we will not apply Niagara retroactively. As we gain experience on a case-by-case basis and hopefully, feasible energy conservation techniques emerge, the applicant, staff, and licensing boards will have obligations to develop an adequate record on these issues in appropriate cases, whether or not they are raised by intervenors.

“However, at this emergent stage of energy conservation principles, intervenors also have their responsibilities. They must state clear and reasonably specific energy conservation contentions in a timely fashion. Beyond that, they have a burden of coming forward with some *535affirmative showing if they wish to have these novel contentions explored further.”12 Id., at 344 (footnotes omitted).

Respondents then challenged the granting of the construction permit in the Court of Appeals for the District of Columbia Circuit.

D

With respect to the challenge of Vermont Yankee’s license, the court first ruled that in the absence of effective rulemaking proceedings,13 the Commission must deal with the environmental impact of fuel reprocessing and disposal in individual licensing proceedings. 178 U. S. App. D. C., at 344, 547 P. 2d, at 641. The court then examined the rulemaking proceedings and, despite the fact that it appeared that the agency employed all the procedures required by 5 U. S. C. § 553 (1976 ed.) and more, the court determined the proceedings to be inadequate and overturned the rule. Accordingly, the Commission’s determination with respect to Vermont Yankee’s license was also remanded for further proceedings.14 178 U. S. App. D. C., at 358, 547 P. 2d, at 6.55.

*536With respect to the permit to Consumers Power, the court first held that the environmental impact statement for construction of the Midland reactors was fatally defective for *537failure to examine energy conservation as an alternative to a plant of this size. 178 U. S. App. D. C., at 331,547F. 2d, at 628. The uourt also thought the report by ACRS was inadequate, although it did not agree that discovery from individual ACRS members was the proper way to obtain further explication of the report. Instead, the court held that the Commission should have sua sponte sent the report back to the ACRS for further elucidation of the “other problems” and their resolution. Id., at 335, 547 F. 2d, at 632. Finally, the court ruled that the fuel cycle issues in this case were controlled by NRDC v. NRC, discussed above, and remanded for appropriate consideration of waste disposal and other unaddressed fuel cycle issues as described in that opinion. 178 U. S. App. D. C., at 335, 547 F. 2d, at 632.

*538II

A

Petitioner Vermont Yankee first argues that the Commission may grant a license to operate a nuclear reactor without any consideration of waste disposal and fuel reprocessing. We find, however, that this issue is no longer presented by the record in this case. The Commission does not contend that it is not required to consider the environmental impact of the spent fuel processes when licensing nuclear power plants. Indeed, the Commission has publicly stated subsequent to the Court of Appeals’ decision in the instant case that consideration of the environmental impact of the back end of the fuel cycle in “the environmental impact statements for individual LWR’s [light-water power reactors] would represent a full and candid assessment of costs and benefits consistent with the legal requirements and spirit of NEPA.” 41 Fed. Reg. 45849 (1976). Even prior to the Court of Appeals’ decision the Commission implicitly agreed that it would consider the back end of the fuel cycle in all licensing proceedings: It indicated that it was not necessary to reopen prior licensing proceedings because “the environmental effects of the uranium fuel cycle have been shown to be relatively insignificant,” and thus incorporation of those effects into the cost-benefit analysis would not change the results of such licensing proceedings. App. 395. Thus, at this stage of the proceedings the only question presented for review in this regard is whether the Commission may consider the environmental impact of the fuel processes when licensing nuclear reactors. In addition to the weight which normally attaches to the agency’s determination of such a question, other reasons support the Commission’s conclusion.

Vermont Yankee will produce annually well over 100 pounds of radioactive wastes, some of which will be highly toxic. The Commission itself, in a pamphlet published by its *539information office, clearly recognizes that these wastes “pose the most severe potential health hazard . . . U. S. Atomic Energy Commission, Radioactive Wastes 12 (1965). Many of these substances must be isolated for anywhere from 600 to hundreds of thousands of years. It is hard to argue that these wastes do not constitute “adverse environmental effects which cannot be avoided should the proposal be implemented,” or that by operating nuclear power plants we are not making “irreversible and irretrievable commitments of resources.” 42 U. S. C. §§ 4332 (2) (C) (ii), (v). As the Court of Appeals recognized, the environmental impact of the radioactive wastes produced by a nuclear power plant is analytically indistinguishable from the environmental effects of “the stack gases produced by a coal-burning power plant.” 178 U. S. App. D. C., at 341, 547 F. 2d, at 638. For these reasons we hold that the Commission acted well within its statutory authority when it considered the back end of the fuel cycle in individual licensing proceedings.

B

We next turn to the invalidation of the fuel cycle rule. But before determining whether the Court of Appeals reached a permissible result, we must determine exactly what result it did reach, and in this case that is no mean feat. Vermont Yankee argues that the court invalidated the rule because of the inadequacy of the procedures employed in the proceedings. Brief for Petitioner in No. 76-419, pp. 30-38. Respondents, on the other hand, labeling petitioner’s view of the decision a “straw man,” argue to this Court that the court merely held that the record was inadequate to enable the reviewing court to determine whether the agency had fulfilled its statutory obligation. Brief for Respondents in No. 76 — A19, pp. 28-30, 40. But we unfortunately have not found the parties’ characterization of the opinion to be entirely reliable; it appears here, as in Orloff v. Willoughby, 345 U. S. 83, 87 (1953), that *540“in this Court the parties changed positions as nimbly as if dancing a quadrille.” 15

After a thorough examination of the opinion itself, we con-*541elude that while the matter is not entirely free from doubt, the majority of the Court of Appeals struck down the rule because of the perceived inadequacies of the procedures employed in the rulemaking proceedings. The court first determined the intervenors’ primary argument to be “that the decision to preclude 'discovery or cross-examination’ denied them a meaningful opportunity to participate in the proceedings as guaranteed by due process.” 178 U. S. App. D. C., at 346, 547 F. 2d, at 643. The court then went on to frame the issue for decision thus:

“Thus, we are called upon to decide whether the procedures provided by the agency were sufficient to ventilate the issues.” Ibid., 547 F. 2d, at 643.

The court conceded that absent extraordinary circumstances it is improper for a reviewing court to prescribe the procedural format an agency must follow, but it likewise clearly thought it entirely appropriate to “scrutinize the record as a whole to insure that genuine opportunities to participate in a meaningful way were provided . . . .” Id., at 347, 547 F. 2d, at 644. The court also refrained from actually ordering the agency to follow any specific procedures, id., at 356-357, 547 F. 2d, at 653-654, but there is little doubt in our minds that *542the ineluctable mandate of the court’s decision is that the procedures afforded during the hearings were inadequate. This conclusion is particularly buttressed by the fact that after the court examined the record, particularly the testimony of Dr. Pittman, and declared it insufficient, the court proceeded to discuss at some length the necessity for further procedural devices or a more “sensitive” application of those devices employed during the proceedings. Ibid. The exploration of the record and the statement regarding its insufficiency might initially lead one to conclude that the court was only examining the sufficiency of the evidence, but the remaining portions of the opinion dispel any doubt that this was certainly not the sole or even the principal basis of the decision. Accordingly, we feel compelled to address the opinion on its own terms, and we conclude that it was wrong.

In prior opinions we have intimated that even in a rule-making proceeding when an agency is making a “ 'quasi-judicial’ ” determination by which a very small number of persons are “ 'exceptionally affected, in each case upon individual grounds,’ ” in some circumstances additional procedures may be required in order to afford the aggrieved individuals due process.16 United States v. Florida East Coast R. Co., 410 U. S., at 242, 245, quoting from Bi-Metallic Investment Co. v. State Board of Equalization, 239 U. S. 441, 446 (1915). It might also be true, although we do not think the issue is presented in this case and accordingly do not decide it, that a totally unjustified departure from well-settled agency procedures of long standing might require judicial correction.17

*543But this much is absolutely clear. Absent constitutional constraints or extremely compelling circumstances the “administrative agencies ‘should be free to fashion their own rules of procedure and to pursue methods of inquiry capable of permitting them to discharge their multitudinous duties.’ ” FCC v. Schreiber, 381 U. S., at 290, quoting from FCC v. Pottsville *544Broadcasting Co., 309 U. S., at 143. Indeed, our cases could hardly be more explicit in this regard. The Court has, as we noted in FCC v. Schreiber, supra, at 290, and n. 17, upheld this principle in a variety of applications,18 including that case where the District Court, instead of inquiring into the validity of the Federal Communications Commission’s exercise of its rulemaking authority, devised procedures to be followed by the agency on the basis of its conception of how the public and private interest involved could best be served. Examining §4 (j) of the Communications Act of 1934, the Court unanimously held that the Court of Appeals erred in upholding that action. And the basic reason for this decision was the Court of Appeals’ serious departure from the very basic tenet of administrative law that agencies should be free to fashion their own rules of procedure.

We have continually repeated this theme through the years, most recently in FPC v. Transcontinental Gas Pipe Line Corp., 423 U. S. 326 (1976), decided just two Terms ago. In that case, in determining the proper scope of judicial review of agency action under the Natural Gas Act, we held that while a court may have occasion to remand an agency decision because of the inadequacy of the record, the agency should normally be allowed to “exercise its administrative discretion in deciding how, in light of internal organization considerations, it may best proceed to develop the needed evidence and how its prior decision should be modified in light of such evidence as develops.” Id., at 333. We went on to emphasize:

“At least in the absence of substantial justification for doing otherwise, a reviewing court may not, after determining that additional evidence is requisite for adequate *545review, proceed by dictating to the agency the methods, procedures, and time dimension of the needed inquiry and ordering the results to be reported to the court without opportunity for further consideration on the basis of the new evidence by the agency. Such a procedure clearly runs the risk of ‘propel [ling] the court into the domain which Congress has set aside exclusively for the administrative agency.’ SEC v. Chenery Corp., 332 U. S. 194, 196 (1947).” Ibid.

Respondent NRDC argues that § 4 of the Administrative Procedure Act, 5 U. S. C. § 553 (1976 ed.), merely establishes lower procedural bounds and that a court may routinely require more than the minimum when an agency’s proposed rule addresses complex or technical factual issues or “Issues of Great Public Import.” Brief for Respondents in No. 76-419, p. 49. We have, however, previously shown that our decisions reject this view. Supra, at 542 to this page. We also think the legislative history, even the part which it cites, does not bear out its contention. The Senate Report explains what eventually became § 4 thus:

“This subsection states . . . the minimum requirements of public rule making procedure short of statutory hearing. Under it agencies might in addition confer with industry advisory committees, consult organizations, hold informal ‘hearings,’ and the like. Considerations of practicality, necessity, and public interest . . . will naturally govern the agency’s determination of the extent to which public proceedings should go. Matters of great import, or those where the public submission of facts will be either useful to the agency or a protection to the public, should naturally be accorded more elaborate public procedures.” S. Rep. No. 752, 79th Cong., 1st Sess., 14-15 (1945).

The House Report is in complete accord:

“ ‘[U]niformity has been found possible and desirable for all classes of both equity and law actions in the courts .... *546It would seem to require no argument to demonstrate that the administrative agencies, exercising but a fraction of the judicial power may likewise operate under uniform rules of practice and procedure and that they may be required to remain within the terms of the law as to the exercise of both quasi-legislative and quasi-judicial power/

“The bill is an outline of minimum essential rights and procedures. ... It affords private parties a means of knowing what their rights are and how they may protect them ....

"... [The bill contains] the essentials of the different forms of administrative proceedings . . . H. R. Rep. No. 1980, 79th Cong., 2d Sess., 9,16-17 (1946).

And the Attorney General’s Manual on the Administrative Procedure Act 31, 35 (1947), a contemporaneous interpretation previously given, some deference by this Court because of the role played by the Department of Justice in drafting the legislation,19 further confirms that view. In short, all of this leaves little doubt that Congress intended that the discretion of the agencies and not that of the courts be exercised in determining when extra procedural devices should be employed.

There are compelling reasons for construing § 4 in this manner. In the first place, if courts continually review agency proceedings to determine whether the agency employed procedures which were, in the court’s opinion, perfectly tailored to reach what the court perceives to be the “best” or “correct” result, judicial review would be totally unpredictable. And the agencies, operating under this vague injunction to employ *547the “best” procedures and facing the threat of reversal if they did not, would undoubtedly adopt full adjudicatory procedures in every instance. Not only would this totally disrupt the statutory scheme, through which Congress enacted “a formula upon which opposing social and political forces have come to rest,” Wong Yang Sung v. McGrath, 339 U. S., at 40, but all the inherent advantages of informal rulemaking would be totally lost.20

Secondly, it is obvious that the court in these cases reviewed the agency’s choice of procedures on the basis of the record actually produced at the hearing, 178 U. S. App. D. C., at 347, 547 F. 2d, at 644, and not on the basis of the information available to the agency when it made the decision to structure the proceedings in a certain way. This sort of Monday morning quarterbacking not only encourages but almost compels the agency to conduct all rulemaking proceedings with the full panoply of procedural devices normally associated only with adjudicatory hearings.

Finally, and perhaps most importantly, this sort of review fundamentally misconceives the nature of the standard for judicial review of an agency rule. The court below uncritically assumed that additional procedures will automatically result in a more adequate record because it will give interested parties more of an opportunity to participate in and contribute to the proceedings. But informal rulemaking need not be based solely on the transcript of a hearing held before an agency. Indeed, the agency need not even hold a formal hearing. See 5 U. S. C. § 553 (c) (1976 ed.). Thus, the adequacy of the “record” in this type of proceeding is not correlated directly to the type of procedural devices employed, but .rather turns on whether the agency has followed the statutory mandate of the Administrative Procedure Act or other relevant statutes. If the agency is compelled to sup*548port the rule which it ultimately adopts with the type of record produced only after a full adjudicatory hearing, it simply will have no choice but to conduct a full adjudicatory hearing prior to promulgating every rule. In sum, this sort of unwarranted judicial examination of perceived procedural shortcomings of a rulemaking proceeding can do nothing but seriously interfere with that process prescribed by Congress.

Respondent NRDC also argues that the fact that the Commission's inquiry was undertaken in the context of NEPA somehow permits a court to require procedures beyond those specified in § 4 of the APA when investigating factual issues through rulemaking. The Court of Appeals was apparently also of this view, indicating that agencies may be required to “develop new procedures to accomplish the innovative task of implementing NEPA through rulemaking. 178 U. S. App. D. C., at 356, 547 F. 2d, at 653. But we search in vain for something in NEPA which would mandate such a result. We have before observed that “NEPA does not repeal by implication any other statute.” Aberdeen & Bockfish B. Co. v. SCRAP, 422 U. S. 289, 319 (1975). See also United States v. SCBAP, 412 U. S. 669, 694 (1973). In fact, just two Terms ago, we emphasized that the only procedural requirements imposed by NEPA are those stated in the plain language of the Act. Kleppe v. Sierra Club, 427 U. S. 390, 405-406 (1976). Thus, it is clear NEPA cannot serve as the basis for a substantial revision of the carefully constructed procedural specifications of the APA.

In short, nothing in the APA, NEPA, the circumstances of this case, the nature of the issues being considered, past agency practice, or the statutory mandate under which the Commission operates permitted the court to review and overturn the rulemaking proceeding on the basis of the procedural devices employed (or not employed) by the Commission so long as the Commission employed at least the statutory minima, a matter about which there is no doubt in this case.

*549There remains, of course, the question of whether the challenged rule finds sufficient justification in the administrative proceedings that it should be upheld by the reviewing court. Judge Tamm, concurring in the result reached by the majority of the Court of Appeals, thought that it did not. There are also intimations in the majority opinion which suggest that the judges who joined it likewise may have thought the administrative proceedings an insufficient basis upon which to predicate the rule in question. We accordingly remand so that the Court of Appeals may review the rule as the Administrative Procedure Act provides. We have made it abundantly clear before that when there is a contemporaneous explanation of the agency decision, the validity of that action must “stand or fall on the propriety of that finding, judged, of course, by the appropriate standard of review. If that finding is not sustainable on the administrative record made, then the Comptroller’s decision must be vacated and the matter remanded to him for further consideration.” Camp v. Pitts, 411 U. S. 138, 143 (1973). See also SEC v. Chenery Corp., 318 U. S. 80 (1943). The court should engage in this kind of review and not stray beyond the judicial province to explore the procedural format or to impose upon the agency its own notion of which procedures are “best” or most likely to further some vague, undefined public good.21

Ill

A

We now turn to the Court of Appeals’ holding “that rejection of energy conservation on the basis of the 'threshold test’ *550was capricious and arbitrary,” 178 U. S. App. D. C., at 332, 547 F. 2d, at 629, and again conclude the court was wrong.

The Court of Appeals ruled that the Commission’s “threshold test” for the presentation of energy conservation contentions was inconsistent with NEPA’s basic mandate to the Commission. Id., at 330, 547 F. 2d, at 627. The Commission, the court reasoned, is something more than an umpire who sits back and resolves adversary contentions at the hearing stage. Ibid., 547 F. 2d, at 627. And when an intervenor’s comments “bring sufficient attention to the issue to stimulate the Commission’s consideration of it,’ ” the Commission must “undertake its own preliminary investigation of the proffered alternative sufficient to reach a rational judgment whether it is worthy of detailed consideration in the EIS. Moreover, the Commission must explain the basis for each conclusion that further consideration of a suggested alternative is unwarranted.” Id., at 331, 547 F. 2d, at 628, quoting from Indiana & Michigan Electric Co. v. FPC, 163 U. S. App. D. C. 334, 337, 502 F. 2d 336, 339 (1974), cert. denied, 420 U. S. 946 (1975).

While the court’s rationale is not entirely unappealing as an abstract proposition, as applied to this case we think it basically misconceives not only the scope of the agency’s statutory responsibility, but also the nature of the administrative process, the thrust of the agency’s decision, and the type of issues the intervenors were trying to raise.

There is little doubt that under the Atomic Energy Act of 1954, state public utility commissions or similar bodies are empowered to make the initial decision regarding the need for power. 42 U. S. C. § 2021 (k). The Commission’s prime area of concern in the licensing context, on the other hand, is national security, public health, and safety. §§ 2132, 2133, 2201. And it is clear that the need, as that term is conventionally used, for the power was thoroughly explored in the hearings. Even the Federal Power Commission, which regu*551lates sales in interstate commerce, 16 U. S. C. § 824 et seq. (1976 ed.), agreed with Consumers Power’s analysis of projected need. App. 207.

NEPA, of course, has altered slightly the statutory balance, requiring “a detailed statement by the responsible official on . . . alternatives to the proposed action.” 42 U. S. C. § 4332 (C). But, as should be obvious even upon a moment’s reflection, the term “alternatives” is not self-defining. To make an impact statement something more than an exercise in frivolous boilerplate the concept of alternatives must be bounded by some notion of feasibility. As the Court of Appeals for the District of Columbia Circuit has itself recognized:

“There is reason for concluding that NEPA was not meant to require detailed discussion of the environmental effects of 'alternatives’ put forward in comments when these effects cannot be readily ascertained and the alternatives are deemed only remote and speculative possibilities, in view of basic changes required in statutes and policies of other agencies — making them available, if at all, only after protracted debate and litigation not meaningfully compatible with the time-frame of the needs to which the underlying proposal is addressed.” Natural Resources Defense Council v. Morton, 148 U. S. App. D. C. 5, 15-16, 458 F. 2d 827, 837-838 (1972).

See also Life of the Land v. Brinegar, 485 F. 2d 460 (CA9 1973), cert. denied, 416 U. S. 961 (1974). Common sense also teaches us that the “detailed statement of alternatives” cannot be found wanting simply because the agency failed to include every alternative device and thought conceivable by the mind of man. ' Time and resources are simply too limited to hold that an impact statement fails because the agency failed to ferret out every possible alternative, regardless of how uncommon or unknown that alternative may have been at the time the project was approved.

*552With these principles in mind we now turn to the notion of “energy conservation,” an alternative the omission of which was thought by the Court of Appeals to have been “forcefully pointed out by Saginaw in its comments on the draft EIS.” 178 U. S. App. D. C., at 328, 547 F. 2d, at 625. Again, as the Commission pointed out, “the phrase 'energy conservation’ has a deceptively simple ring in this context. Taken literally, the phrase suggests a virtually limitless range of possible actions and developments that might, in one way or another, ultimately reduce projected demands for electricity from a particular proposed plant.” App. 331. Moreover, as a practical matter, it is hard to dispute the observation that it is largely the events of recent years that have emphasized not only the need but also a large variety of alternatives for energy conservation. Prior to the drastic oil shortages incurred by the United States in 1973, there was little serious thought in most Government circles of energy conservation alternatives. Indeed, the Council on Environmental Quality did not promulgate regulations which even remotely suggested the need to consider energy conservation in impact statements until August 1, 1973. See 40 CFR § 1500.8 (a) (4) (1977); 38 Fed. Reg. 20554 (1973). And even then the guidelines were not made applicable to draft and final statements filed with the Council before January 28, 1974. Id., at 20557, 21265. The Federal Power Commission likewise did not require consideration of energy conservation in applications to build hydroelectric facilities until June 19, 1973. 18 CFR pt. 2, App. A., §8.2 (1977); 38 Fed. Reg. 15946, 15949 (1973). And these regulations were not made retroactive either. Id., at 15946. All this occurred over a year and a half after the draft environmental statement for Midland had been prepared, and over a year after the final environmental statement had been prepared and the hearings completed.

We think these facts amply demonstrate that the concept of “alternatives” is an evolving one, requiring the agency to *553explore more or fewer alternatives as they become better known and understood. This was well understood by the Commission, which, unlike the Court of Appeals, recognized that the Licensing Board’s decision had to be judged by the information then available to it. And judged in that light we have little doubt the Board’s actions were well within the proper bounds of its statutory authority. Not only did the record before the agency give every indication that the project was actually needed, but also there was nothing before the Board to indicate to the contrary.

We also think the court’s criticism of the Commission’s “threshold test” displays a lack of understanding of the historical setting within which the agency action took place and of the nature of the test itself. In the first place, while it is true that NEPA places upon an agency the obligation to consider every significant aspect of the environmental impact of a proposed action, it is still incumbent upon intervenors who wish to participate to structure their participation so that it is meaningful, so that it alerts the agency to the intervenors’ position and contentions. This is especially true when the intervenors are requesting the agency to embark upon an exploration of uncharted territory, as was the question of energy conservation in the late 1960’s and early 19'70’s.

“[C]omments must be significant enough to step over a threshold requirement of materiality before any lack of agency response or consideration becomes of concern. The comment cannot merely state that a particular mistake was made ... ; it must show why the mistake was of possible significance in the results . . . .” Portland Cement Assn. v. Ruckelshaus, 158 U. S. App. D. C. 308, 327, 486 F. 2d 375, 394 (1973), cert. denied sub nom. Portland Cement Corp. v. Administrator, EPA, 417 U. S. 921 (1974).

Indeed, administrative proceedings should not be a game or a forum to engage in unjustified obstructionism by making *554cryptic and obscure reference to matters that “ought to' be” considered and then, after failing to do more to bring the matter to the agency’s attention, seeking to have that agency determination vacated on the ground that the agency failed to consider matters “forcefully presented.” In fact, here the agency continually invited further clarification of Saginaw’s contentions. Even without such clarification it indicated a willingness to receive evidence on the matters. But not only did Saginaw decline to further focus its contentions, it virtually declined to participate, indicating that it had “no conventional findings of fact to set forth” and that it had not “chosen to search the record and respond to this proceeding by submitting citations of matter which we believe were proved or disproved.”

We also think the court seriously mischaracterized the Commission’s “threshold test” as placing “heavy substantive burdens ... on intervenors . . . .” 178 U. S. App. D. C., at 330, and n. 11, 547 F. 2d, at 627, and n. 11. On the contrary, the Commission explicitly stated:

“We do not equate this burden with the civil litigation concept of a prima jade case, an unduly heavy burden in this setting. But the showing should be sufficient to require reasonable minds to inquire further.” App. 344 n. 27.

We think this sort of agency procedure well within the agency’s discretion.

In sum, to characterize the actions of the Commission as “arbitrary or capricious” in light of the facts then available to it as described at length above, is to deprive those words of any meaning. As we have said in the past:

“Administrative consideration of evidence . . . always creates a gap between the time the record is closed and the time the administrative decision is promulgated [and, we might add, the time the decision is judicially reviewed]. ... If upon the coming down of the order *555litigants might demand rehearings as a matter of law because some new circumstance has arisen, some new trend has been observed, or some new fact discovered, there would be little hope that the administrative process could ever be consummated in an order that would not be subject to reopening.” ICC v. Jersey City, 322 U. S. 503, 514 (1944).

See also Northern Lines Merger Cases, 396 U. S. 491, 521 (1970).

We have also made it clear that the role of a court in reviewing the sufficiency of an agency’s consideration of environmental factors is a limited one, limited both by the time at which the decision was made and by the statute mandating review.

“Neither the statute nor its legislative history contemplates that a court should substitute its judgment for that of the agency as to the environmental consequences of its actions.” Kleppe v. Sierra Club, 427 U. S., at 410 n. 21.

We think the Court of Appeals has forgotten that injunction here and accordingly its judgment in this respect must also be reversed.22

*556B

Finally, we turn to the Court of Appeals’ holding that the Licensing Board should have returned the ACRS report to ACRS for further elaboration, understandable to a layman, of the reference to other problems.

The Court of Appeals reasoned that since one function of the report was “that all concerned may be apprised of the safety or possible hazard of the facilities,” the report must be in terms understandable to a layman and replete with cross-references to previous reports in which the “other problems” are detailed. Not only that, but if the report does not so elaborate, and the Licensing Board fails to sun sponte return the report to ACRS for further development, the entire agency action, made after exhaustive studies, reviews, and 14 days of hearings, must be nullified.

Again the Court of Appeals has unjustifiably intruded into the administrative process. It is true that Congress thought publication of the ACRS report served an important function. But the legislative history shows that the function of publication was subsidiary to its main function, that of providing technical advice from a body of experts uniquely qualified to provide assistance. See 42 U. S. C. § 2039; S. Rep. No. 296, 85th Cong., 1st Sess., 24 (1957); Joint Committee on Atomic Energy, A Study of AEC Procedures and Organization in the Licensing of Reactor Facilities, 85th Cong., 1st Sess., 32-34 (Comm. Print 1957). The basic information to be conveyed to the public is not necessarily a full technical exposition of every facet of nuclear energy, but rather the ACRS’s position, and reasons therefor, with respect to the safety of a proposed nuclear reactor. Accordingly, the ACRS cannot be faulted for not dealing with every facet of nuclear energy in every report it issues.

Of equal significance is the fact that the ACRS was not obfuscating its findings. The reports to which it referred were matters of public record, on file in the Commission’s *557public-documents room. Indeed, all ACRS reports are on file there. Furthermore, we are informed that shortly after the Licensing Board’s initial decision, ACRS prepared a list which identified its “generic safety concerns.” In light of all this it is simply inconceivable that a reviewing court should find it necessary or permissible to order the Board to sua sponte return the report to ACRS. Our view is confirmed by the fact that the putative reason for the remand was that the public did not understand the report, and yet not one member of the supposedly uncomprehending public even asked that the report be remanded. This surely is, as petitioner Consumers Power claims, “judicial intervention run riot.” Brief for Petitioner in No. 76-528, p. 37.

We also think it worth noting that we find absolutely nothing in the relevant statutes to justify what the court did here. The Commission very well might be able to remand a report for further clarification, but there is nothing to support a court’s ordering the Commission to take that step or to support a court’s requiring the ACRS to give a short explanation, understandable to a layman, of each generic safety concern.

All this leads us to make one further observation of some relevance to this case. To say that the Court of Appeals’ final reason for remanding is insubstantial at best is a gross understatement. Consumers Power first applied in 1969 for a construction permit — not even an operating license, just a construction permit. The proposed plant underwent an incredibly extensive review. The reports filed and reviewed literally fill books. The proceedings took years, and the actual hearings themselves over two weeks. To then nullify that effort seven years later because one report refers to other problems, which problems admittedly have been discussed at length in-other reports available to the public, borders on the Kafkaesque. Nuclear energy may some day be a cheap, safe source of power or it may not. But Congress has made a *558choice to at least try nuclear energy, establishing a reasonable review process in which courts are to play only a limited role. The fundamental policy questions appropriately resolved in Congress and in the state legislatures are not subject to reexamination in the federal courts under the guise of judicial review of agency action. Time may prove wrong the decision to develop nuclear energy, but it is Congress or the States within their appropriate agencies which must eventually make that judgment. In the meantime courts should perform their appointed function. NEPA does set forth significant substantive goals for the Nation, but its mandate to the agencies is essentially procedural. See 42 IT. S. C. § 4332. See also Aberdeen & Bockfish R. Co. v. SCRAP, 422 U. S., at 319. It is to insure a fully informed and well-considered decision, not necessarily a decision the judges of the Court of Appeals or of this Court would have reached had they been members of the decisionmaking unit of the agency. Administrative decisions should be set aside in this context, as in every other, only for substantial procedural or substantive reasons as mandated by statute, Consolo v. FMC, 383 U. S. 607, 620 (1966), not simply because the court is unhappy with the result reached. And a single alleged oversight on a peripheral issue, urged by parties who never fully cooperated or indeed raised the issue below, must not be made the basis for overturning a decision properly made .after an otherwise exhaustive proceeding.

Reversed and remanded.

Mr. Justice Blackmun and Mr. Justice Powell took no part in the consideration or decision of these cases.