delivered the opinion of the Court.

Respondent is a producer and distributor of advertising motion pictures which depict and describe commodities offered for sale by commercial establishments. Respondent contracts with theatre owners for the display of these advertising films and ships the films from its place of business in Louisiana to theatres in twenty-seven states and the District of Columbia. These contracts run for terms up to five years, the majority being for one or two years. A substantial number of them contain a provision that the theatre owner will display only advertising films furnished by respondent, with the exception of films for charities or for governmental organizations, or announcements of coming attractions. Respondent and three other companies in the same business (against which proceedings were also brought) together had exclusive arrangements for advertising films with approximately three-fourths of the total number of theatres in the United States which display advertising films for compensation. Respondent had exclusive contracts with almost 40 percent of the theatres in the area where it operates.

The Federal Trade Commission, the petitioner, filed a complaint charging respondent with the use of “unfair methods of competition” in violation of § 5 of the Federal Trade Commission Act, 38 Stat. 717, 719, 52 Stat. *394Ill, 15 U. S. C. § 45. The Commission found that respondent was in substantial competition with other companies engaged in the business of distributing advertising films, that its exclusive contracts have limited the outlets for films of competitors and have forced some competitors out of business because of their inability to obtain outlets for their advertising films. It held by a divided vote that the exclusive contracts are unduly restrictive of competition when they extend for periods in excess of one year. It accordingly entered a cease and desist order which prohibits respondent from entering into any such contract that grants an exclusive privilege for more than a year or from continuing in effect any exclusive provision of an existing contract longer than a year after the date of service in the Commission’s order.1 47 F. T. C. 378. The Court of Appeals reversed, holding that the exclusive contracts are not unfair methods of competition and that their prohibition would not be in the public interest. 194 F. 2d 633.

The “unfair methods of competition,” which are condemned by § 5 (a) of the Act, are not confined to those that were illegal at common law or that were condemned by the Sherman Act. Federal Trade Commission v. Keppel & Bro., 291 U. S. 304. Congress advisedly left the concept flexible to be defined with particularity by the myriad of cases from the field of business. Id., pp. 310-312. It is also clear that the Federal Trade Commission Act was designed to supplement and bolster the Sherman Act and the Clayton Act (see Federal Trade Commission v. Beech-Nut Co., 257 U. S. 441, 453) — to stop in their incipiency acts and practices which, when full blown, *395would violate those Acts (see Fashion Guild v. Federal Trade Commission, 312 U. S. 457, 463, 466), as well as to condemn as “unfair methods of competition” existing violations of them. See Federal Trade Commission v. Cement Institute, 333 U. S. 683, 691.

The Commission found in the present case that respondent’s exclusive contracts unreasonably restrain competition and tend to monopoly. Those findings are supported by substantial evidence. This is not a situation where by the nature of the market there is room for newcomers, irrespective of the existing restrictive practices. The number of outlets for the films is quite limited. And due to the exclusive contracts, respondent and the three other major companies have foreclosed to competitors 75 percent of all available outlets for this business throughout the United States. It is, we think, plain from the Commission’s findings that a device which has sewed up a market so tightly for the benefit of a few falls within the prohibitions of the Sherman Act and is therefore an “unfair method of competition” within the meaning of § 5 (a) of the Federal Trade Commission Act.

An attack is made on that part of the order which restricts the exclusive contracts to one-year terms. It is argued that one-year contracts will not be practicable. It is said that the expenses of securing these screening contracts do not warrant one-year agreements, that investment of capital in the business would not be justified without assurance of a market for more than one year, that theatres frequently demand guarantees for more than a year or otherwise refuse to exhibit advertising films. These and other business requirements are the basis of the argument that exclusive contracts of a duration in excess of a year are necessary for the conduct of the business of the distributors. The Commission considered this argument and concluded that, although the exclusive contracts were beneficial to the distributor and preferred *396by the theatre owners, their use should be restricted in the public interest. The Commission found that the term of one year had become a standard practice and that the continuance of exclusive contracts so limited would not be an undue restraint upon competition, in view of the compelling business reasons for some exclusive arrangement.2 The precise impact of a particular practice on the trade is for the Commission, not the courts, to determine. The point where a method of competition becomes “unfair” within the meaning of the Act will often turn on the exigencies of a particular situation, trade practices, or the practical requirements of the business in question. Certainly we cannot say that exclusive contracts in this field should have been banned in their entirety or not at all, that the Commission exceeded the limits of its allowable judgment (see Siegel Co. v. Federal Trade Commission, 327 U. S. 608, 612; Federal Trade Commission v. Cement Institute, 333 U. S. 683, 726-727) in limiting their term to one year.3

*397The Court of Appeals held that the contracts between respondent and the theatres were contracts of agency and therefore governed by Federal Trade Commission v. Curtis Publishing Co., 260 U. S. 568. This was on the theory that respondent furnishes the films by bailment to the exhibitors in exchange for a contract for personal services which the exhibitors undertake to perform. But the Curtis case would be relevant here only if § 3 of the Clayton Act4 were involved. The vice of the exclusive contract in this particular field is in its tendency to restrain competition and to develop a monopoly in violation of the Sherman Act. And when the Sherman Act is involved the crucial fact is the impact of the particular practice on competition, not the label that it carries. See United States v. Masonite Corp., 316 U. S. 265, 280.

Finally, respondent urges that the sole issue raised in the Commission’s complaint had been adjudicated in a former proceeding instituted by the Commission which resulted in a cease and desist order. 36 F. T. C. 957. *398But that was a proceeding to put an end to a conspiracy between respondent and other distributors involving the use of these exclusive agreements. The present proceeding charges no conspiracy; it is directed against individual acts of respondent. The plea of res judicata is therefore not available since the issues litigated and determined in the present case are not the same as those in the earlier one. Cf. Tait v. Western Maryland R. Co., 289 U. S. 620, 623.

Reversed.

dissenting.

My doubts that the Commission has adequately shown that it has been guided by relevant criteria in dealing with its findings under § 5 of the Federal Trade Commission Act are dispelled neither by those findings nor by the opinion of the Court. The Commission has not explained its conclusion with the “simplicity and clearness” necessary to tell us “what a decision means before the duty becomes ours to say whether it is right or wrong.” United States v. Chicago, M., St. P. & P. R. Co., 294 U. S. 499, 510, 511.

My primary concern is that the Commission has not related its analysis of this industry to the standards of illegality in § 5 with sufficient clarity to enable this Court to review the order. Although we are told that respondent and three other companies have exclusive exhibition contracts with three-quarters of the theaters in the country that accept advertising, there are no findings indicating how many of these contracts extend beyond the one-year period which the Commission finds not unduly restrictive. We do have an indication from the record that more than half of respondent’s exclusive contracts run for only one year; if that is so, that part of respondent’s hold on the market found unreasonable by the *399Commission boils down to exclusion of other competitors from something like 1,250 theaters, or about 6%, of the some 20,000 theaters in the country. The hold is on about 10% of the theaters that accept advertising.

Apart from uncritical citations in the brief here,1 the Commission merely states a dogmatic conclusion that the use of these contracts constitutes an “unreasonable restraint and restriction of competition.” In re Motion Picture Advertising Service Co., 47 F. T. C. 378, 389. The Court’s opinion is merely an echo of this conclusion and states without discussion that such exclusion from a market without more “falls within the prohibitions of the Sherman Act” because, taken with exclusive contracts of other competitors, 75% of the market is shut off. But there is no reliance here on conspiracy or concerted action to foreclose the market, a charge that would of course warrant action under the Sherman Law. Indeed, we must assume that respondent and the other three companies are complying with an earlier order of the Commission directed at concerted action. See In re Screen Broadcast Corp., 36 F. T. C. 957. While the existence of the other exclusive contracts is, of course, *400not irrelevant in a market analysis, see Standard Oil Co. v. United States, 337 U. S. 293, 309, this Court has never decided that they may, in the absence of conspiracy, be aggregated to support a charge of Sherman Law violation. Cf. id., at 314. If other factors pertinent to a Sherman Law violation were present here, the Commission could not leave such factors unmentioned and simply ask us to review a broad unexplained finding that there is such a violation.2 In any event, the Commission has not found any Sherman Law violation.

But we are told, as is of course true, that § 5 of the Federal Trade Commission Act comprehends more than violations of the Sherman Law. The Federal Trade Commission Act was designed, doubtless, to enable the *401Commission to nip in the bud practices which, when full blown, would violate the Sherman or Clayton Act. But this record does not explain to us how these practices, if full blown, would violate one of those Acts. The Commission has been content to rest on its conclusion that respondent’s exclusive contracts unreasonably restrain competition and tend to monopoly. If judicial review is to have a basis for functioning, the Commission must do more than pronounce a conclusion by way of fiat and without explication. This is not a tribunal for investigating an industry. Analysis of practices in the light of definable standards of illegality is for the Commission. It is for us to determine whether the Commission has correctly applied the proper standards and thus exhibited that familiarity with competitive problems which the Congress anticipated the Commission would achieve from its experience. Cf. Federal Trade Commission v. Cement Institute, 333 U. S. 683, 727.

No case is called to our attention which, because of factual similarity, would serve as a shorthand elucidation of the Commission’s conclusion. The Standard Oil case, supra, relied on in the Commission’s brief, does not serve this purpose. Although the Standard Oil case was brought under § 3 of the Clayton Act, I shall assume that it could have been brought under § 5 of the Federal Trade Commission Act, so that respondent cannot argue the inapplicability of the decision merely because the language of § 3 may be inapplicable. But taking that case simply as an expression of “policy” underlying § 5, it is not sufficient to support the holding in this case. In the Standard Oil case, we dealt with the largest seller of gasoline in its market; Standard had entered into exclusive supply contracts with 16% of the retail outlets in the area purchasing over $57,000,000 worth of gasoline. It may be that considerations undisclosed could be advanced to indicate that the percentage of the market *402shut off here, calculated by a juggling of imponderables that we certainly would not confidently weigh without expert guidance, ought not to be considered significantly different from that in the Standard Oil case, or perhaps more important in the light of that decision, see 337 U. S., at 314, that the aggregate volume of business is of as great significance to the public as it was there. Even so, there are apparent differences whose effects we would need to have explained.

The obvious bargaining power of the seller vis-a-vis the retailer does not, so far as we are advised, have a parallel here. Nor are we apprised by proof or analysis to disregard the fact that here the advertising, unlike sales of gasoline by the retailer in the Standard Oil case, is not the central business of the theaters and apparently accounts for only a small part of the theaters’ revenues.3 In any event, in the Standard Oil case we recognized the discrepancy in bargaining power and pointed out that the retailers might still insist on exclusive contracts if they wanted. See 337 U. S., at 314. And although we are not told in this case whether the pressure for exclusive contracts comes mainly from the distributor or the theater, there are indications that theaters often insist on exclusive provisions. See Findings as to the Facts No. 12, In re Motion Picture Advertising Service Co., supra, at 388.

Further, the findings of the Commission indicate that there are some factual differences in the “exclusive” pro*403visions here, for in this industry, as may not have been feasible in gasoline retailing, distributors of films often do have access to the theaters having nominally exclusive contracts with competing distributors. At times the exclusive provision may do little more than give the distributor a priority over other distributors in the use of screen space. Indeed, the degree of exclusion of competitors in some instances is represented simply by the inadequacy of a 15% commission paid the “excluded” competitor when he is permitted to show his films in theaters nominally exclusive. The Commission found the 15% unprofitable in local advertising, but it did not find how much of the affected competitors’ total business, which may also have included manufacturer-dealer or cooperative advertising and national advertising, was in effect excluded because of the unprofitability of the commission in local advertising. In short, we are not told that the exclusive feature here should be considered the economic equivalent of that in the Standard Oil case.

Although the facts of this case do not meet the Standard Oil decision, even if that case is taken merely as an expression of antitrust policy engrafted on § 5, it is urged that the Commission should be allowed ample discretion in developing the law of unfair methods of competition to meet the exigencies of a particular situation without undue hampering by the Court. But if judicial review is to have any meaning, extension of principle to meet new situations must be based on some minimum demonstration to the courts that the Commission has relied on relevant criteria to conclude that the new application is in the public interest. In this case, apart from equivocal statements in the Trial Examiner’s report on the evidence as to the interests affected by exclusion from this market, we have no specific indication of the need for enforcement in this area, cf. Federal Trade Commission v. Keppel & Bro., 291 U. S. 304, 314, even if the Com*404mission had afforded reasons why the law of unfair methods of competition should strike down exclusive contracts such as those here involved. At the least, we should remand this case to the Commission for adequate explanation of the reasons why the public interest requires its intervention and this order.4 Cf. Federal Trade Commission v. Klesner, 280 U. S. 19.

It is of great importance to bear in mind that the determination of the scope of the prohibition of “unfair methods of competition” has not been left to the administrative agency as part of its fact-finding authority but is a matter of law to be defined by the courts. See Federal Trade Commission v. Gratz, 253 U. S. 421, 427. The significance of such judicial review may be indicated by the dissimilar treatment of comparable standards entrusted to the enforcement of the Interstate Commerce Commission. In dealing with the provisions of the Interstate Commerce Act requiring reasonableness in rates and practices from carriers subject to the control of the Commerce Commission, we read the Act as making the application of standards of reasonableness a determination of fact by that Commission and not an issue of law for the courts. Unlike the Federal Trade Commission Act, the Interstate Commerce Act dealt with governmental regulation not only of a limited sector of the economy but of economic enterprises that had long been singled out for public control. The range within which the broadly stated concepts of reasonable*405ness moved was confined as well as defined by experience, and application of the concepts was necessarily limited to easily comparable economic activity. On the other hand, the Federal Trade Commission Act gave an administrative agency authority over economic controls of a different sort that began with the Sherman Law— restrictions upon the whole domain of economic enterprise engaged in interstate commerce. The content of the prohibition of “unfair methods of competition,” to be applied to widely diverse business practices, was not entrusted to the Commission for ad hoc determination within the interstices of individualized records but was left for ascertainment by this Court.

The vagueness of the Sherman Law was saved by imparting to it the gloss of history. See Nash v. United States, 229 U. S. 373. Difficulties with this inherent uncertainty in the Sherman Law led to the particulariza-tions expressed in the Clayton Act. 38 Stat. 730. The creation of the Federal Trade Commission, 38 Stat. 717, made available a continuous administrative process by which fruition of Sherman Law violations could be aborted. But it is another thing to suggest that anything in business activity that may, if unchecked, offend the particularizations of the Clayton Act may now be reached by the Federal Trade Commission Act. The curb on the Commission’s power, as expressed by the series of cases beginning with the Gratz case, supra, so as to leave to the courts rather than the Commission the final authority in determining what is an unfair method of competition, would be relaxed, and unbridled intervention into business practices encouraged.

I am not unaware that the policies directed at maintaining effective competition, as expressed in the Sherman Law, the Clayton Act, as amended by the Robinson-Patman Act, and the Federal Trade Commission Act, are difficult to formulate and not altogether harmonious. *406Therefore, the interpretation of the Acts by the agency which is constantly engaged in construing them should carry considerable weight with courts even in the solution of the legal puzzles these statutes raise. But he is no friend of administrative law who thinks that the Commission should be left at large. In any event, whatever problems would be raised by withholding judicial review from determinations of the Commission are for Congress to face, at least in the first instance. (See my views expressed in Stark v. Wickard, 321 U. S. 288, 311.) Until Congress chooses to do so, we cannot shirk our duty by leaving determinations of law to the discretion of the Federal Trade Commission. Not only must we abstain from approving a mere say-so of the Commission and thus fail to discharge the task implied by judicial review. It is also incumbent upon us to seek to rationalize the four statutes directed toward a common end and make of them, to the extent that what Congress has written permits, a harmonious body of law. This opinion is an attempt, at least by way of adumbration, to carry out this aim.

I would have the Court of Appeals remand this case to the Commission.