Target (Ds), competing beer wholesalers, by some miracle all decided at the same time to stop giving Ps, retailers, interest-free credit related to purchases of product. Ps allege that beginning in early 1967, Ds secretly agreed, in order to eliminate competition among themselves, that as of December 1967, they would sell to Ps only if payment were made in advance or upon delivery. Prior to the agreement, the wholesalers had extended credit without interest up to the 30- and 42-day limits permitted by state law. Ps were a conditionally certified class of beer retailers who brought suit against Ds alleging that they had conspired to eliminate short-term trade credit formerly granted on beer purchases in violation of § 1 of the Sherman Act. The District Court entered an interlocutory order, which denied Ps' 'motion to declare this a case of per se illegality.' The court then certified to the Court of Appeals for the Ninth Circuit, pursuant to 28 U. S. C. § 1292 (b) the question. The Court of Appeals agreed with the District Court that a horizontal agreement among competitors to fix credit terms does not necessarily contravene the antitrust laws. Ps appealed.