delivered the opinion of the Court.

We granted certiorari to determine whether a parent corporation and its wholly owned subsidiary are legally capable of conspiring with each other under § 1 of the Sherman Act.

I

A.

The predecessor to petitioner Regal Tube Co. was established in Chicago in 1955 to manufacture structural steel *756tubing used in heavy equipment, cargo vehicles, and construction. From 1955 to 1968 it remained a wholly owned subsidiary of C. E. Robinson Co. In 1968 Lear Siegler, Inc., purchased Regal Tube Co. and operated it as an unincorporated division. David Grohne, who had previously served as vice president and general manager of Regal, became president of the division after the acquisition.

In 1972 petitioner Copperweld Corp. purchased the Regal division from Lear Siegler; the sale agreement bound Lear Siegler and its subsidiaries not to compete with Regal in the United States for five years. Copperweld then transferred Regal’s assets to a newly formed, wholly owned Pennsylvania corporation, petitioner Regal Tube Co. The new subsidiary continued to conduct its manufacturing operations in Chicago but shared Copperweld’s corporate headquarters in Pittsburgh.

Shortly before Copperweld acquired Regal, David Grohne accepted a job as a corporate officer of Lear Siegler. After the acquisition, while continuing to work for Lear Siegler, Grohne set out to establish his own steel tubing business to compete in the same market as Regal. In May 1972 he formed respondent Independence Tube Corp., which soon secured an offer from the Yoder Co. to supply a tubing mill. In December 1972 respondent gave Yoder a purchase order to have a mill ready by the end of December 1973.

When executives at Regal and Copperweld learned of Grohne’s plans, they initially hoped that Lear Siegler’s non-competition agreement would thwart the new competitor. Although their lawyer advised them that Grohne was not bound by the agreement, he did suggest that petitioners might obtain an injunction against Grohne’s activities if he made use of any technical information or trade secrets belonging to Regal. The legal opinion was given to Regal and Copperweld along with a letter to be sent to anyone with whom Grohne attempted to deal. The letter warned that Copperweld would be “greatly concerned if [Grohne] contem*757plates entering the structural tube market... in competition with Regal Tube” and promised to take “any and all steps which are necessary to protect our rights under the terms of our purchase agreement and to protect the know-how, trade secrets, etc., which we purchased from Lear Siegler.” Petitioners later asserted that the letter was intended only to prevent third parties from developing reliance interests that might later make a court reluctant to enjoin Grohne’s operations.

When Yoder accepted respondent’s order for a tubing mill on February 19, 1973, Copperweld sent Yoder one of these letters; two days later Yoder voided its acceptance. After respondent’s efforts to resurrect the deal failed, respondent arranged to have a mill supplied by another company, which performed its agreement even though it too received a warning letter from Copperweld. Respondent began operations on September 13,1974, nine months later than it could have if Yoder had supplied the mill when originally agreed.

Although the letter to Yoder was petitioners’ most successful effort to discourage those contemplating doing business with respondent, it was not their only one. Copperweld repeatedly contacted banks that were considering financing respondent’s operations. One or both petitioners also approached real estate firms that were considering providing plant space to respondent and contacted prospective suppliers and customers of the new company.

B

In 1976 respondent filed this action in the District Court against petitioners and Yoder.1 The jury found that *758Copperweld and Regal had conspired to violate §1 of the Sherman Act, 26 Stat. 209, as amended, 15 U. S. C. § 1, but that Yoder was not part of the conspiracy. It also found that Copperweld, but not Regal, had interfered with respondent’s contractual relationship with Yoder; that Regal, but not Copperweld, had interfered with respondent’s contractual relationship with a potential customer of respondent, Deere Plow & Planter Works, and had slandered respondent to Deere; and that Yoder had breached its contract to supply a tubing mill.

At a separate damages phase, the judge instructed the jury that the damages for the antitrust violation and for the inducement of the Yoder contract breach should be identical and not double counted. The jury then awarded $2,499,009 against petitioners on the antitrust claim, which was trebled to $7,497,027. It awarded $15,000 against Regal alone on the contractual interference and slander counts pertaining to Deere. The court also awarded attorney’s fees and costs after denying petitioners’ motions for judgment n.o.v. and for a new trial.

C

The United States Court of Appeals for the Seventh Circuit affirmed. 691 F. 2d 310 (1982). It noted that the exoneration of Yoder from antitrust liability left a parent corporation and its wholly owned subsidiary as the only parties to the § 1 conspiracy. The court questioned the wisdom of subjecting an “intra-enterprise” conspiracy to antitrust liability, when the same conduct by a corporation and an unincorpo*759rated division would escape liability for lack of the requisite two legal persons. However, relying on its decision in Photovest Corp. v. Fotomat Corp., 606 F. 2d 704 (1979), cert. denied, 445 U. S. 917 (1980), the Court of Appeals held that liability was appropriate “when there is enough separation between the two entities to make treating them as two independent actors sensible.” 691 F. 2d, at 318. It held that the jury instructions took account of the proper factors for determining how much separation Copperweld and Regal in fact maintained in the conduct of their businesses.2 It also held that there was sufficient evidence for the jury to conclude that Regal was more like a separate corporate entity than a mere service arm of the parent.

We granted certiorari to reexamine the intra-enterprise conspiracy doctrine, 462 U. S. 1131 (1983), and we reverse.

Review of this case calls directly into question whether the coordinated acts of a parent and its wholly owned subsidiary can, in the legal sense contemplated by § 1 of the Sherman Act, constitute a combination or conspiracy.3 The so-called “intra-enterprise conspiracy” doctrine provides that § 1 liability is not foreclosed merely because a parent and its subsidiary are subject to common ownership. The doctrine derives from declarations in several of this Court’s opinions.

*760In no case has the Court considered the merits of the intra-enterprise conspiracy doctrine in depth. Indeed, the concept arose from a far narrower rule. Although the Court has expressed approval of the doctrine on a number of occasions, a finding of intra-enterprise conspiracy was in all but perhaps one instance unnecessary to the result.

The problem began with United States v. Yellow Cab Co., 332 U. S. 218 (1947). The controlling shareholder of the Checker Cab Manufacturing Corp., Morris Markin, also controlled numerous companies operating taxicabs in four cities. With few exceptions, the operating companies had once been independent and had come under Markin’s control by acquisition or merger. The complaint alleged conspiracies under §§ 1 and 2 of the Sherman Act among Markin, Checker, and five corporations in the operating system. The Court stated that even restraints in a vertically integrated enterprise were not “necessarily” outside of the Sherman Act, observing that an unreasonable restraint

“may result as readily from a conspiracy among those who are affiliated or integrated under common ownership as from a conspiracy among those who are otherwise independent. Similarly, any affiliation or integration flowing from an illegal conspiracy cannot insulate the conspirators from the sanctions which Congress has imposed. The corporate interrelationships of the conspirators, in other words, are not determinative of the applicability of the Sherman Act. That statute is aimed at substance rather than form. See Appalachian Coals, Inc. v. United States, 288 U. S. 344, 360-361, 376-377.

“And so in this case, the common ownership and control of the various corporate appellees are impotent to liberate the alleged combination and conspiracy from the impact of the Act. The complaint charges that the restraint of interstate trade was not only effected by the combination of the appellees but was the primary object *761of the combination. The theory of the complaint... is that ‘dominating power’ over the cab operating companies ‘was not obtained by normal expansion . . . but by deliberate, calculated purchase for control.’” Id., at 227-228 (emphasis added) (quoting United States v. Reading Co., 253 U. S. 26, 57 (1920)).

It is the underscored language that later breathed life into the intra-enterprise conspiracy doctrine. The passage as a whole, however, more accurately stands for a quite different proposition. It has long been clear that a pattern of acquisitions may itself create a combination illegal under § 1, especially when an original anticompetitive purpose is evident from the affiliated corporations’ subsequent conduct.4 The Yellow Cab passage is most fairly read in light of this settled rule. In Yellow Cab, the affiliation of the defendants was irrelevant because the original acquisitions were themselves illegal.5 An affiliation “flowing from an illegal conspiracy” would not avert sanctions. Common ownership and control were irrelevant because restraint of trade was “the primary object of the combination,” which was created in a “‘delib*762erate, calculated’ ” manner. Other language in the opinion is to the same effect.6

The Court’s opinion relies on Appalachian Coals, Inc. v. United States, 288 U. S. 344 (1933); however, examination of that case reveals that it gives very little support for the broad doctrine Yellow Cab has been thought to announce. On the contrary, the language of Chief Justice Hughes speaking for the Court in Appalachian Coals supports a contrary conclusion. After observing that “[t]he restrictions the Act imposes are not mechanical or artificial,” 288 U. S., at 360, he went on to state:

*763“The argument that integration may be considered a normal expansion of business, while a combination of independent producers in a common selling agency should be treated as abnormal — that one is a legitimate enterprise and the other is not — makes but an artificial distinction. The Anti-Trust Act aims at substance.” Id., at 377.7

As we shall see, infra, at 771-774, it is the intra-enterprise conspiracy doctrine itself that “makes but an artificial distinction” at the expense of substance.

The ambiguity of the Yellow Cab holding yielded the one case giving support to the intra-enterprise conspiracy doctrine.8 In Kiefer-Stewart Co. v. Joseph E. Seagram & Sons, Inc., 340 U. S. 211 (1951), the Court held that two wholly owned subsidiaries of a liquor distiller were guilty under § 1 of the Sherman Act for jointly refusing to supply a wholesaler who declined to abide by a maximum resale pricing scheme. The Court offhandedly dismissed the defendants’ argument *764that “their status as ‘mere instrumentalities of a single manufacturing-merchandizing unit’ makes it impossible for them to have conspired in a manner forbidden by the Sherman Act.” Id., at 215. With only a citation to Yellow Cab and no further analysis, the Court stated that the

“suggestion runs counter to our past decisions that common ownership and control does not liberate corporations from the impact of the antitrust laws”

and stated that this rule was “especially applicable” when defendants “hold themselves out as competitors.” 340 U. S., at 215.

Unlike the Yellow Cab passage, this language does not pertain to corporations whose initial affiliation was itself unlawful. In straying beyond Yellow Cab, the Kiefer-Stewart Court failed to confront the anomalies an intra-enterprise doctrine entails. It is relevant nonetheless that, were the ease decided today, the same result probably could be justified on the ground that the subsidiaries conspired with wholesalers other than the plaintiff.9 An intra-enterprise conspiracy doctrine thus would no longer be necessary to a finding of liability on the facts of Kiefer-Stewart.

Later cases invoking the intra-enterprise conspiracy doctrine do little more than cite Yellow Cab or Kiefer-Stewart, and in none of the cases was the doctrine necessary to the result reached. Timken Roller Bearing Co. v. United States, 341 U. S. 593 (1951), involved restrictive horizontal agree*765ments between an American corporation and two foreign corporations in which it owned 30 and 50 percent interests respectively. The Timken Court cited Kiefer Stewart to show that “[t]he fact that there is common ownership or control of the contracting corporations does not liberate them from the impact of the antitrust laws.” 341 U. S., at 598. But the relevance of this statement is unclear. The American defendant in Timken did not own a majority interest in either of the foreign corporate conspirators and, as the District Court found, it did not control them.10 Moreover, as in Yellow Cab, there was evidence that the stock acquisitions were themselves designed to effectuate restrictive practices.11 The Court’s reliance on the intra-enterprise conspiracy doctrine was in no way necessary to the result.

The same is true of Perma Life Mufflers, Inc. v. International Parts Corp., 392 U. S. 134 (1968), which involved a conspiracy among a parent corporation and three subsidiaries to impose various illegal restrictions on plaintiff franchisees. The Court did suggest that, because the defendants

“availed themselves of the privilege of doing business through separate corporations, the fact of common own*766ership could not save them from any of the obligations that the law imposes on separate entities [citing Yellow Cab and Timken].” Id., at 141-142.

But the Court noted immediately thereafter that “[i]n any event” each plaintiff could “clearly” charge a combination between itself and the defendants or between the defendants and other franchise dealers. Ibid. Thus, for the same reason that a finding of liability in Kiefer-Stewart could today be justified without reference to the intra-enterprise conspiracy doctrine, see n. 9, supra, the doctrine was at most only an alternative holding in Perma Life Mufflers.

In short, while this Court has previously seemed to acquiesce in the intra-enterprise conspiracy doctrine, it has never explored or analyzed in detail the justifications for such a rule; the doctrine has played only a relatively minor role in the Court’s Sherman Act holdings.

III

Petitioners, joined by the United States as amicus curiae, urge us to repudiate the intra-enterprise conspiracy doctrine. 12 The central criticism is that the doctrine gives undue significance to the fact that a subsidiary is separately incorporated and thereby treats as the concerted activity of two *767entities what is really unilateral behavior flowing from decisions of a single enterprise.

We limit our inquiry to the narrow issue squarely presented: whether a parent and its wholly owned subsidiary are capable of conspiring in violation of § 1 of the Sherman Act. We do not consider under what circumstances, if any, a parent may be liable for conspiring with an affiliated corporation it does not completely own.

A

The Sherman Act contains a “basic distinction between concerted and independent action.” Monsanto Co. v. Spray-Rite Service Corp., 465 U. S. 752, 761 (1984). The conduct of a single firm is governed by § 2 alone and is unlawful only when it threatens actual monopolization.13 It is not enough that a single firm appears to “restrain trade” unreasonably, for even a vigorous competitor may leave that impression. For instance, an efficient firm may capture unsatisfied customers from an inefficient rival, whose own ability to compete may suffer as a result. This is the rule of the marketplace and is precisely the sort of competition that promotes the consumer interests that the Sherman Act aims to foster.14 In part because it is sometimes difficult to *768distinguish robust competition from conduct with long-run anticompetitive effects, Congress authorized Sherman Act scrutiny of single firms only when they pose a danger of monopolization. Judging unilateral conduct in this manner reduces the risk that the antitrust laws will dampen the competitive zeal of a single aggressive entrepreneur.

Section 1 of the Sherman Act, in contrast, reaches unreasonable restraints of trade effected by a "contract, combination ... or conspiracy” between separate entities. It does not reach conduct that is “wholly unilateral.” Albrecht v. Herald Co., 390 U. S. 145, 149 (1968); accord, Monsanto Co. v. Spray-Rite Corp., supra, at 761. Concerted activity subject to § 1 is judged more sternly than unilateral activity under §2. Certain agreements, such as horizontal price fixing and market allocation, are thought so inherently anti-competitive that each is illegal per se without inquiry into the harm it has actually caused. See generally Northern Pacific R. Co. v. United States, 356 U. S. 1, 5 (1958). Other combinations, such as mergers, joint ventures, and various vertical agreements, hold the promise of increasing a firm’s efficiency and enabling it to compete more effectively. Accordingly, such combinations are judged under a rule of reason, an inquiry into market power and market structure designed to assess the combination’s actual effect. See, e. g., Continental T. V., Inc. v. GTE Sylvania Inc., 433 U. S. 36 (1977); Chicago Board of Trade v. United States, 246 U. S. 231 (1918). Whatever form the inquiry takes, however, it is not necessary to prove that concerted activity threatens monopolization.

The reason Congress treated concerted behavior more strictly than unilateral behavior is readily appreciated. Concerted activity inherently is fraught with anticompetitive *769risk. It deprives the marketplace of the independent centers of decisionmaking that competition assumes and demands. In any conspiracy, two or more entities that previously pursued their own interests separately are combining to act as one for their common benefit. This not only reduces the diverse directions in which economic power is aimed but suddenly increases the economic power moving in one particular direction. Of course, such mergings of resources may well lead to efficiencies that benefit consumers, but their anticompetitive potential is sufficient to warrant scrutiny even in the absence of incipient monopoly.

B

The distinction between unilateral and concerted conduct is necessary for a proper understanding of the terms “contract, combination ... or conspiracy” in § 1. Nothing in the literal meaning of those terms excludes coordinated conduct among officers or employees of the same company. But it is perfectly plain that an internal “agreement” to implement a single, unitary firm’s policies does not raise the antitrust dangers that § 1 was designed to police. The officers of a single firm are not separate economic actors pursuing separate economic interests, so agreements among them do not suddenly bring together economic power that was previously pursuing divergent goals. Coordination within a firm is as likely to result from an effort to compete as from an effort to stifle competition. In the marketplace, such coordination may be necessary if a business enterprise is to compete effectively. For these reasons, officers or employees of the same firm do not provide the plurality of actors imperative for a §1 conspiracy.16

*770There is also general agreement that § 1 is not violated by the internally coordinated conduct of a corporation and one of its unincorporated divisions.16 Although this Court has not previously addressed the question,17 there can be little doubt that the operations of a corporate enterprise organized into divisions must be judged as the conduct of a single actor. The existence of an unincorporated division reflects no more than a firm’s decision to adopt an organizational division of labor. A division within a corporate structure pursues the common interests of the whole rather than interests separate from those of the corporation itself; a business enterprise establishes divisions to further its own interests in the most efficient manner. Because coordination between a corporation *771and its division does not represent a sudden joining of two independent sources of economic power previously pursuing separate interests, it is not an activity that warrants § 1 scrutiny.

Indeed, a rule that punished coordinated conduct simply because a corporation delegated certain responsibilities to autonomous units might well discourage corporations from creating divisions with their presumed benefits. This would serve no useful antitrust purpose but could well deprive consumers of the efficiencies that decentralized management may bring.

C

For similar reasons, the coordinated activity of a parent and its wholly owned subsidiary must be viewed as that of a single enterprise for purposes of § 1 of the Sherman Act. A parent and its wholly owned subsidiary have a complete unity of interest. Their objectives are common, not disparate; their general corporate actions are guided or determined not by two separate corporate consciousnesses, but one. They are not unlike a multiple team of horses drawing a vehicle under the control of a single driver. With or without a formal “agreement,” the subsidiary acts for the benefit of the parent, its sole shareholder. If a parent and a wholly owned subsidiary do “agree” to a course of action, there is no sudden joining of economic resources that had previously served different interests, and there is no justification for § 1 scrutiny.

Indeed, the very notion of an “agreement” in Sherman Act terms between a parent and a wholly owned subsidiary lacks meaning. A § 1 agreement may be found when “the conspirators had a unity of purpose or a common design and understanding, or a meeting of minds in an unlawful arrangement.” American Tobacco Co. v. United States, 328 U. S. 781, 810 (1946). But in reality a parent and a wholly owned subsidiary always have a “unity of purpose or a common design.” They share a common purpose whether or not the parent keeps a tight rein over the subsidiary; the parent may assert *772full control at any moment if the subsidiary fails to act in the parent’s best interests.18

The intra-enterprise conspiracy doctrine looks to the form of an enterprise’s structure and ignores the reality. Antitrust liability should not depend on whether a corporate subunit is organized as an unincorporated division or a wholly owned subsidiary. A corporation has complete power to maintain a wholly owned subsidiary in either form. The economic, legal, or other considerations that lead corporate management to choose one structure over the other are not relevant to whether the enterprise’s conduct seriously threatens competition.19 Rather, a corporation may adopt the subsidiary form of organization for valid management and related purposes. Separate incorporation may im*773prove management, avoid special tax problems arising from multistate operations, or serve other legitimate interests.20 Especially in view of the increasing complexity of corporate operations, a business enterprise should be free to structure itself in ways that serve efficiency of control, economy of operations, and other factors dictated by business judgment without increasing its exposure to antitrust liability. Because there is nothing inherently anticompetitive about a corporation’s decision to create a subsidiary, the intra-enterprise conspiracy doctrine “impose[s] grave legal consequences upon organizational distinctions that are of de minimis meaning and effect.” Sunkist Growers, Inc. v. Winckler & Smith Citrus Products Co., 370 U. S. 19, 29 (1962).21

If antitrust liability turned on the garb in which a corporate subunit was clothed, parent corporations would be encouraged to convert subsidiaries into unincorporated divisions. Indeed, this is precisely what the Seagram company did after this Court’s decision in Kiefer-Stewart Co. v. Joseph E. Seagram & Sons, Inc., 340 U. S. 211 (1951).22 Such an *774incentive serves no valid antitrust goals but merely deprives consumers and producers of the benefits that the subsidiary form may yield.

The error of treating a corporate division differently from a wholly owned subsidiary is readily seen from the facts of this case. Regal was operated as an unincorporated division of Lear Siegler for four years before it became a wholly owned subsidiary of Copperweld. Nothing in this record indicates any meaningful difference between Regal’s operations as a division and its later operations as a separate corporation. Certainly nothing suggests that Regal was a greater threat to competition as a subsidiary of Copperweld than as a division of Lear Siegler. Under either arrangement, Regal might have acted to bar a new competitor from entering the market. In one case it could have relied on economic power from other quarters of the Lear Siegler corporation; instead it drew on the strength of its separately incorporated parent, Copperweld. Prom the standpoint of the antitrust laws, there is no reason to treat one more harshly than the other. As Chief Justice Hughes cautioned, “[idealities must dominate the judgment.” Appalachian Coals, Inc. v. United States, 288 U. S., at 360.23

D

Any reading of the Sherman Act that remains true to the Act’s distinction between unilateral and concerted conduct will necessarily disappoint those who find that distinction arbitrary. It cannot be denied that § l’s focus on concerted *775behavior leaves a “gap” in the Act’s proscription against unreasonable restraints of trade. See post, at 789. An unreasonable restraint of trade may be effected not only by two independent firms acting in concert; a single firm may restrain trade to precisely the same extent if it alone possesses the combined market power of those same two firms. Because the Sherman Act does not prohibit unreasonable restraints of trade as such — but only restraints effected by a contract, combination, or conspiracy — it leaves untouched a single firm’s anticompetitive conduct (short of threatened monopolization) that may be indistinguishable in economic effect from the conduct of two firms subject to § 1 liability.

*774“It is the unlawful combination, tested by the rules of common law and human experience, that is aimed at by this bill, and not the lawful and useful combination.” 21 Cong. Rec. 2457 (1890).

*775We have already noted that Congress left this “gap” for eminently sound reasons. Subjecting a single firm’s every action to judicial scrutiny for reasonableness would threaten to discourage the competitive enthusiasm that the antitrust laws seek to promote. See supra, at 767-769. Moreover, whatever the wisdom of the distinction, the Act’s plain language leaves no doubt that Congress made a purposeful choice to accord different treatment to unilateral and concerted conduct. Had Congress intended to outlaw unreasonable restraints of trade as such, § l’s requirement of a contract, combination, or conspiracy would be superfluous, as would the entirety of §2.24 Indeed, this Court has recog*776nized that § 1 is limited to concerted conduct at least since the days of United States v. Colgate & Co., 250 U. S. 300 (1919). Accord, post, at 789.

The appropriate inquiry in this case, therefore, is not whether the coordinated conduct of a parent and its wholly owned subsidiary may ever have anticompetitive effects, as the dissent suggests. Nor is it whether the term “conspiracy” will bear a literal construction that includes parent corporations and their wholly owned subsidiaries. For if these were the proper inquiries, a single firm’s conduct would be subject to § 1 scrutiny whenever the coordination of two employees was involved. Such a rule would obliterate the Act’s distinction between unilateral and concerted conduct, contrary to the clear intent of Congress as interpreted by the weight of judicial authority. See n. 15, supra. Rather, the appropriate inquiry requires us to explain the logic underlying Congress’ decision to exempt unilateral conduct from § 1 scrutiny, and to assess whether that logic similarly excludes the conduct of a parent and its wholly owned subsidiary. Unless we second-guess the judgment of Congress to limit § 1 to concerted conduct, we can only conclude that the coordinated behavior of a parent and its wholly owned subsidiary falls outside the reach of that provision.

Although we recognize that any “gap” the Sherman Act leaves is the sensible result of a purposeful policy decision by Congress, we also note that the size of any such gap is open *777to serious question. Any anticompetitive activities of corporations and their wholly owned subsidiaries meriting antitrust remedies may be policed adequately without resort to an intra-enterprise conspiracy doctrine. A corporation’s initial acquisition of control will always be subject to scrutiny under § 1 of the Sherman Act and § 7 of the Clayton Act, 38 Stat. 731, 15 U. S. C. §18. Thereafter, the enterprise is fully subject to § 2 of the Sherman Act and § 5 of the Federal Trade Commission Act, 38 Stat. 719, 15 U. S. C. §45. That these statutes are adequate to control dangerous anticompet-itive conduct is suggested by the fact that not a single holding of antitrust liability by this Court would today be different in the absence of an intra-enterprise conspiracy doctrine. It is further suggested by the fact that the Federal Government, in its administration of the antitrust laws, no longer accepts the concept that a corporation and its wholly owned subsidiaries can “combine” or “conspire” under § l.25 Elimination of the intra-enterprise conspiracy doctrine with respect to corporations and their wholly owned subsidiaries will therefore not cripple antitrust enforcement. It will simply eliminate treble damages from private state tort suits masquerading as antitrust actions.

IV

We hold that Copperweld and its wholly owned subsidiary Regal are incapable of conspiring with each other for purposes of § 1 of the Sherman Act. To the extent that prior decisions of this Court are to the contrary, they are disapproved and overruled. Accordingly, the judgment of the Court of Appeals is reversed.

It is so ordered.

dissenting.

It is safe to assume that corporate affiliates do not vigorously compete with one another. A price-fixing or market-allocation agreement between two or more such corporate entities does not, therefore, eliminate any competition that would otherwise exist. It makes no difference whether such an agreement is labeled a “contract,” a “conspiracy,” or merely a policy decision, because it surely does not unreasonably restrain competition within the meaning of the Sherman Act. The Rule of Reason has always given the courts adequate latitude to examine the substance rather than the form of an arrangement when answering the question whether collective action has restrained competition within the meaning of § 1.

Today the Court announces a new per se rule: a wholly owned subsidiary is incapable of conspiring with its parent under §1 of the Sherman Act. Instead of redefining the word “conspiracy,” the Court would be better advised to continue to rely on the Rule of Reason. Precisely because they do not eliminate competition that would otherwise exist but rather enhance the ability to compete, restraints which enable effective integration between a corporate parent and its subsidiary — the type of arrangement the Court is properly concerned with protecting — are not prohibited by § 1. Thus, the Court’s desire to shield such arrangements from antitrust liability provides no justification for the Court’s new rule.

In contrast, the case before us today presents the type of restraint that has precious little to do with effective integration between parent and subsidiary corporations. Rather, the purpose of the challenged conduct was to exclude a potential competitor of the subsidiary from the market. The jury apparently concluded that the two defendant corporations— *779Copperweld and its subsidiary Regal — had successfully delayed Independence’s entry into the steel tubing business by applying a form of economic coercion to potential suppliers of financing and capital equipment, as well as to potential customers. Everyone seems to agree that this conduct was tortious as a matter of state law. This type of exclusionary conduct is plainly distinguishable from vertical integration designed to achieve competitive efficiencies. If, as seems to be the case, the challenged conduct was manifestly anti-competitive, it should not be immunized from scrutiny under § 1 of the Sherman Act.

h — I

Repudiation of prior cases is not a step that should be taken lightly. As the Court wrote only days ago: “[A]ny departure from the doctrine of stare decisis demands special justification.” Arizona v. Rumsey, ante, at 212. It is therefore appropriate to begin with an examination of the precedents.

In United States v. Yellow Cab Co., 332 U. S. 218 (1947), the Court explicitly stated that a corporate subsidiary could conspire with its parent:

“The fact that these restraints occur in a setting described by the appellees as a vertically integrated enterprise does not necessarily remove the ban of the Sherman Act. The test of illegality under the Act is the presence or absence of an unreasonable restraint on interstate commerce. Such a restraint may result as readily from a conspiracy among those who are affiliated or integrated under common ownership as from a conspiracy among those who are otherwise independent.” Id., at 227.

The majority attempts to explain Yellow Cab by suggesting that it dealt only with unlawful acquisition of subsidiaries. Ante, at 761-762. But the Court mentioned acquisitions only as an additional consideration separate from the passage *780quoted above,1 and more important, the Court explicitly held that restraints imposed by the corporate parent on the affiliates that it already owned in themselves violated § l.2

At least three cases involving the motion picture industry also recognize that affiliated corporations may combine or conspire within the meaning of §1. In United States v. Crescent Amusement Co., 323 U. S. 173 (1944), as the Court recognizes, ante, at 762, n. 6, the only conspirators were affiliated corporations. The majority’s claim that the case involved only unlawful acquisitions because of the Court’s comments concerning divestiture of the affiliates cannot be squared with the passage immediately following that cited by the majority, which states that there had been unlawful conduct going beyond the acquisition of subsidiaries:

“That principle is adequate here to justify divestiture of all interest in some of the affiliates since their acquisition was part of the fruits of the conspiracy. But the relief need not, and under these facts should not, be so restricted [to divestiture]. The fact that the companies were affiliated induced joint action and agreement. Common control was one of the instruments in bringing about unity of purpose and unity of action and in making the conspiracy effective. If that affiliation continues, *781there will be tempting opportunity for these exhibitors to continue to act in combination against the independents.” 323 U. S., at 189-190 (emphasis supplied).

Similarly, in Schine Chain Theatres, Inc. v. United States, 334 U. S. 110 (1948), the Court held that concerted action by parents and subsidiaries constituted an unlawful conspiracy.3 That was also the holding in United States v. Griffith, 334 U. S. 100, 109 (1948). The majority’s observation that in these cases there were alternative grounds that could have been used to reach the same result, ante, at 763, n. 8, disguises neither the fact that the holding that actually appears in these opinions rests on conspiracy between affiliated entities, nor that today’s holding is inconsistent with what was actually held in these cases.

In Kiefer-Stewart Co. v. Joseph E. Seagram & Sons, Inc., 340 U. S. 211 (1951), the Court’s holding was plain and unequivocal: *782This holding is so clear that even the Court, which is not wanting for inventiveness in its reading of the prior cases, cannot explain it away. The Court suggests only that today Kiefer-Stewart might be decided on alternative grounds, ante, at 764, ignoring the fact that today’s holding is inconsistent with the ground on which the case actually was decided.4

*781“Respondents next suggest that their status as ‘mere in-strumentalities of a single manufacturing-merchandizing unit’ makes it impossible for them to have conspired in a manner forbidden by the Sherman Act. But this suggestion runs counter to our past decisions that common ownership and control does not liberate corporations from the impact of the antitrust laws. E. g. United States v. Yellow Cab Co., 332 U. S. 218. The rule is especially applicable where, as here, respondents hold themselves out as competitors.” Id., at 215.

*782A construction of the statute that reaches agreements between corporate parents and subsidiaries was again embraced by the Court in Timken Roller Bearing Co. v. United States, 341 U. S. 598 (1951),5 and Perma Life Mufflers, Inc. v. International Parts Corp., 392 U. S. 134 (1968).6 The majority only notes that there might have been . other grounds for decision available in these cases, ante, at 764-766, but again it cannot deny that its new rule is inconsistent with what the Court actually did write in these cases.

*783Thus, the rule announced today is inconsistent with what this Court has held on at least seven previous occasions.7 Perhaps most illuminating is the fact that until today, whether they favored the doctrine or not, it had been the universal conclusion of both the lower courts8 and the commentators9 that this Court’s cases establish that a parent *784and a wholly owned subsidiary corporation are capable of conspiring in violation of § 1. In this very case the Court of Appeals observed:

“[T]he salient factor is that the Supreme Court’s decisions, while they need not be read with complete literalism, of course they cannot be ignored. It is no accident that every Court of Appeals to consider the question has concluded that a parent and its subsidiary have the same capacity to conspire, whether or not they can be found to have done so in a particular case.” 691 F. 2d 310, 317 (CA7 1982) (footnotes omitted).

Thus, we are not writing on a clean slate. “[W]e must bear in mind that considerations of stare decisis weigh heavily in the area of statutory construction, where Congress is free to change this Court’s interpretation of its legislation.” Illinois Brick Co. v. Illinois, 431 U. S. 720, 736 (1977).10 There can be no doubt that the Court today changes what has been taken to be the long-settled rule: a rule that Congress did not revise at any point in the last four decades. At a minimum there should be a strong presumption against the approach taken today by the Court. It is to the merits of that approach that I now turn.

II

The language of § 1 of the Sherman Act is sweeping m its breadth: “Every contract, combination in the form of trust or *785otherwise, or conspiracy, in restraint of trade or commerce among the several States, ... is declared to be illegal.” 15 U. S. C. § 1. This Court has long recognized that Congress intended this language to have a broad sweep, reaching any form of combination:

“[I]n view of the. many new forms of contracts and combinations which were being evolved from existing economic conditions, it was deemed essential by an all-embracing enumeration to make sure that no form of contract or combination by which an undue restraint of interstate or foreign commerce was brought about could save such restraint from condemnation. The statute under this view evidenced the intent not to restrain the right to make and enforce contracts, whether resulting from combination or otherwise, which did not unduly restrain interstate or foreign commerce, but to protect that commerce from being restrained by methods, whether old or new, which would constitute an interference that is an undue restraint.” Standard Oil Co. v. United States, 221 U. S. 1, 59-60 (1911).

This broad construction is illustrated by the Court’s refusal to limit the statute to actual agreements. Even mere acquiescence in an anticompetitive scheme has been held sufficient to satisfy the statutory language.11

Since the statute was written against the background of the common law,12 reference to the common law is particularly enlightening in construing the statutory requirement of a “contract, combination in the form of trust or otherwise, or conspiracy.” Under the common law, the question whether *786affiliated corporations constitute a plurality of actors within the meaning of the statute is easily answered. The well-settled rule is that a corporation is a separate legal entity; the separate corporate form cannot be disregarded.13 The Congress that passed the Sherman Act was well acquainted with this rule. See 21 Cong. Rec. 2571 (1890) (remarks of Sen. Teller) (“Each corporation is a creature by itself”). Thus it has long been the law of criminal conspiracy that the officers of even a single corporation are capable of conspiring with each other or the corporation.14 This Court has held that a corporation can conspire with its employee,15 and that a labor union can “combine” with its business agent within the meaning of § l.16 This concept explains the Timken Court’s statement that the affiliated corporations in that case made *787“agreements between legally separate persons,” 341 U. S., at 598. Thus, today’s holding that agreements between parent and subsidiary corporations involve merely unilateral conduct is at odds with the way that this Court has traditionally understood the concept of a combination or conspiracy, and also at odds with the way in which the Congress that enacted the Sherman Act surely understood it.

Holding that affiliated corporations cannot constitute a plurality of actors is also inconsistent with the objectives of the Sherman Act. Congress was particularly concerned with “trusts,” hence it named them in § 1 as a specific form of “combination” at which the statute was directed. Yet “trusts” consisted of affiliated corporations. As Senator Sherman explained:

“Because these combinations are always in many States and, as the Senator from Missouri says, it will be very easy for them to make a corporation within a State. So they can; but that is only one corporation of the combination. The combination is always of two or more, and in one case of forty-odd corporations, all bound together by a link which holds them under the name of trustees, who are themselves incorporated under the laws of one of the States.” 21 Cong. Rec. 2569 (1890).

The activities of these “combinations” of affiliated corporations were of special concern:

“[Associated enterprise and capital are not satisfied with partnerships and corporations competing with each other, and have invented a new form of combination commonly called trusts, that seeks to avoid competition by combining the controlling corporations, partnerships, and individuals engaged in the same business, and placing the power and property of the combination under the government of a few individuals, and often under the control of a single man called a trustee, a chairman, or a president.

*788“The sole object of such a combination is to make competition impossible. It can control the market, raise or lower prices, as will best promote its selfish interests, reduce prices in a particular locality and break down competition and advance prices at will where competition does not exist. Its governing motive is to increase the profits of the parties composing it. The law of selfishness, uncontrolled by competition, compels it to disregard the interest of the consumer. It dictates terms to transportation companies, it commands the price of labor without fear of strikes, for in its field it allows no competitors. ... It is this kind of a combination we have to deal with now.” Id., at 2457.17

Thus, the corporate subsidiary, when used as a device to eliminate competition, was one of the chief evils to which the Sherman Act was addressed.18 The anomaly in today’s holding is that the corporate devices most similar to the original “trusts” are now those which free an enterprise from antitrust scrutiny.

*789h — ( I — ( l-H

The Court s reason for rejecting the concept of a combination or conspiracy among a parent corporation and its wholly owned subsidiary is that it elevates form over substance— while in form the two corporations are separate legal entities, in substance they are a single integrated enterprise and hence cannot comprise the plurality of actors necessary to satisfy §1. Ante, at 771-774. In many situations the Court’s reasoning is perfectly sensible, for the affiliation of corporate entities often is procompetitive precisely because, as the Court explains, it enhances efficiency. A challenge to conduct that is merely an incident of the desirable integration that accompanies such affiliation should fail. However, the protection of such conduct provides no justification for the Court’s new rule, precisely because such conduct cannot be characterized as an unreasonable restraint of trade violative of § 1. Conversely, the problem with the Court’s new rule is that it leaves a significant gap in the enforcement of § 1 with respect to anticompetitive conduct that is entirely unrelated to the efficiencies associated with integration.

Since at least United States v. Colgate & Co., 250 U. S. 300 (1919), § 1 has been construed to require a plurality of actors. This requirement, however, is a consequence of the plain statutory language, not of any economic principle. As an economic matter, what is critical is the presence of market power, rather than a plurality of actors.19 From a competitive standpoint, a decision of a single firm possessing power to reduce output and raise prices above competitive levels has the same consequence as a decision by two firms acting together who have acquired an equivalent amount of market *790power through an agreement not to compete.20 Unilateral conduct by a firm with market power has no less anticompet-itive potential than conduct by a plurality of actors which generates or exploits the same power,21 and probably more, since the unilateral actor avoids the policing problems faced by cartels.

The rule of Yellow Cab thus has an economic justification. It addresses a gap in antitrust enforcement by reaching anti-competitive agreements between affiliated corporations which *791have sufficient market power to restrain marketwide competition, but not sufficient power to be considered monopolists within the ambit of §2 of the Act.22 The doctrine is also useful when a third party declines to join a conspiracy to restrain trade among affiliated corporations, and is harmed as a result through a boycott or similar tactics designed to penalize the refusal. In such cases, since there has been no agreement with the third party, only an agreement between the affiliated corporations can be the basis for § 1 inquiry.23 Finally, it must be remembered that not all persons who restrain trade wear grey flannel suits. Businesses controlled by organized crime often attempt to gain control of an industry through violence or intimidation of competitors; in such cases § 1 can be applied to separately incorporated businesses which benefit from such tactics, but which may be ultimately controlled by a single criminal enterprise.24

*792The rule of Yellow Cab and its progeny is not one that condemns every parent-subsidiary relationship. A single firm, no matter what its corporate structure may be, is not expected to compete with itself.25 Functional integration by its very nature requires unified action; hence in itself it has never been sufficient to establish the existence of an unreasonable restraint of trade: “In discussing the charge in the Yellow Cab case, we said that the fact that the conspirators were integrated did not insulate them from the act, not that corporate integration violated the act.” United States v. Columbia Steel Co., 334 U. S. 495, 522 (1948). Restraints that act only on the parent or its subsidiary as a consequence of an otherwise lawful integration do not violate § 1 of the Sherman Act.26 But if the behavior at issue is unrelated to any functional integration between the affiliated corporations and *793imposes a restraint on third parties of sufficient magnitude to restrain marketwide competition, as a matter of economic substance, as well as form, it is appropriate to characterize the conduct as a “combination or conspiracy in restraint of trade.”27

For example, in Yellow Cab the Court read the complaint as alleging that integration had assisted the parent in excluding competing manufacturers from the marketplace, 332 U. S., at 226-227, leading the Court to conclude that “restraint of interstate trade was not only effected by the combination of the appellees but was the primary object of the combination.” Id., at 227. Similarly, in Crescent Amusement the Court noted that corporate affiliation between exhibitors enhanced their buying power and “was one of the instruments in . . . making the conspiracy effective” in excluding independents from the market. 323 U. S., at 189-190. Thus, in both cases the Court found that the affiliation enhanced the ability of the parent corporation to exclude the competition of third parties, and hence raised entry *794barriers faced by actual and potential competitors. When conduct restrains trade not merely by integrating affiliated corporations but rather by restraining the ability of others to compete, that conduct has competitive significance drastically different from procompetitive integration.28 In these cases, the affiliation assisted exclusionary conduct; it was not the competitive equivalent of unilateral integration but instead generated power to restrain marketwide competition.

There are other ways in which corporate affiliation can operate to restrain competition. A wholly owned subsidiary might market a “fighting brand” or engage in other predatory behavior that would be more effective if its ownership were concealed than if it was known that only one firm was involved. A predator might be willing to accept the risk of bankrupting a subsidiary when it could not afford to let a division incur similar risks. Affiliated corporations might enhance their power over suppliers by agreeing to refuse to deal with those who deal with an actual or potential com*795petitor of one of them; such a threat might be more potent coming from both corporations than from only one.29

In this case, it may be that notices to potential suppliers of respondent emanating from Copperweld carried more weight than would notices coming only from Regal. There was evidence suggesting that Regal and Copperweld were not integrated, and that the challenged agreement had little to do with achieving procompetitive efficiencies and much to do with protecting Regal’s market position. The Court does not even try to explain why their common ownership meant that Copperweld and Regal were merely obtaining benefits associated with the efficiencies of integration. Both the District Court and the Court of Appeals thought that their agreement had a very different result — that it raised barriers to entry and imposed an appreciable marketwide restraint. The Court’s discussion of the justifications for corporate affiliation is therefore entirely abstract — while it dutifully lists the procompetitive justifications for corporate affiliation, ante, at 772-774, it fails to explain how any of them relate to the conduct at issue in this case. What is challenged here is not the fact of integration between Regal and Copperweld, but their specific agreement with respect to Independence. That agreement concerned the exclusion of *796Independence from the market, and not any efficiency resulting from integration. The facts of this very case belie the conclusion that affiliated corporations are incapable of engaging in the kind of conduct that threatens marketwide competition. The Court does not even attempt to assess the competitive significance of the conduct under challenge here — it never tests its economic assumptions against the concrete facts before it. Use of economic theory without reference to the competitive impact of the particular economic arrangement at issue is properly criticized when it produces overly broad per se rules of antitrust liability;30 criticism is no less warranted when a per se rule of antitrust immunity is adopted in the same way.

In sum, the question that the Court should ask is not why a wholly owned subsidiary should be treated differently from a corporate division, since the immunity accorded that type of arrangement is a necessary consequence of Colgate. Rather the question should be why two corporations that engage in a predatory course of conduct which produces a marketwide restraint on competition and which, as separate legal entities, can be easily fit within the language of § 1, should be immunized from liability because they are controlled by the same godfather. That is a question the Court simply fails to confront. I respectfully dissent.