a preliminary injunction may be granted without any showing that the plaintiff would suffer irreparable injury without such relief. Despite the overall flexibility of the test for preliminary injunctive relief, and the discretion vested in the district court, equity has traditionally required such irreparable harm before an interlocutory injunction may be issued. See Rondeau v. Mosinee Paper Corp., 422 U.S. 49, 61, 64-65, 95 S.Ct. 2069, 2077, 2078-2079, 45 L.Ed.2d 12 (1975); Sampson v. Murray, 415 U.S. 61, 88, 94 S.Ct. 937, 951, 39 L.Ed.2d 166 (1974); Beacon Theatres v. Westover, 359 U.S. 500, 506-07, 79 S.Ct. 948, 954, 3 L.Ed.2d 988 (1959); E.E.O.C. v. Hocking Corp., 666 F.2d 1037, 1039 (6th Cir. Dec. 16, 1981); United States v. Spectro Foods Corp., 544 F.2d 1175, 1181 (3rd Cir. 1976); 11 Wright & Miller, Federal Practice and Procedure § 2948, pp. 430-441 (1973); see generally Leubsdorf, The Standard For Preliminary Injunctions, 91 Harv.L.Rev. 525, 527-37 (1978). In Sampson v. Murray, supra, the Supreme Court reversed the granting of a preliminary injunction, in part because the plaintiff had not made any showing of irreparable harm. The Court stated:
We believe that the Court of Appeals was quite wrong in suggesting that at this stage of the proceeding the District Court need not have concluded that there was actually irreparable injury. This Court has stated that “[t]he basis of injunctive relief in the federal courts has always been irreparable harm and inadequacy of legal remedies” .... Yet the record before us indicates that no witnesses were heard on the issue of irreparable injury, that respondent’s complaint was not verified, and that the affidavit she submitted to the District Court did not touch in any way upon considerations relevant to irreparable injury.
415 U.S. at 88, 94 S.Ct. at 951 (citations omitted).
The requirement of irreparable harm to support the granting of a preliminary injunction applies to private antitrust actions in the same way it applies to equity actions in general. This is made clear, both implicitly and explicitly, by section 16 of the Clayton Act, 15 U.S.C. § 26 (1976), which provides:
Any person, firm, corporation, or association shall be entitled to sue for and have injunctive relief, in any court of the United States having jurisdiction over the parties, against threatened loss or damage by a violation of the antitrust laws, ... when and under the same conditions and principles as injunctive relief against threatened conduct that will cause loss or damage is granted by courts of equity, under the rules governing such proceedings, and upon the execution of proper bond against damages for an injunction improvidently granted and a showing that the danger of irreparable loss or damage is immediate, a preliminary injunction may issue....
(emphasis added). Accord, Dataphase Systems, Inc. v. CL Systems, Inc., 640 F.2d 109, 114 (8th Cir. 1981) (en banc); Triebwasser & Katz v. American Telephone & Telegraph Co., 535 F.2d 1356, 1359 (2d Cir. 1976); Automatic Radio Mfg. Co. v. Ford Motor Co., 390 F.2d 113, 116 (1st Cir.), cert. denied, 391 U.S. 914, 88 S.Ct. 1807, 20 L.Ed.2d 653 (1968); II Areeda & Turner, Antitrust Law § 329, pp. 138-39 (1978); 15 Von Kalinowski, Antitrust Laws and Trade Regulation § 114.01[1], pp. 114-2, 114-6, 114 — 7 (1981).
II
In granting Friendship’s motion for a preliminary injunction, the district court appears to have employed the so-called “alternate” test which has been recognized by several circuits. Otherwise known as the “balance of hardships” test, the alternate test requires a showing of “sufficiently serious questions going to the merits to make them a fair ground for litigation and a balance of hardships tipping decidedly toward the party requesting the preliminary relief.” Sonesta Int’l Hotels Corp. v. Wellington Associates, 483 F.2d 247, 250 (2d Cir. 1973) (emphasis in original). Our review of the record convinces us that the district judge viewed the alternate test as eliminating the traditional requirement of irreparable injury whenever the balance of harms