In 1998, Texaco Inc. (Texaco) (defendant) and Shell Oil Company (Shell) (defendant) engaged in a joint venture to sell gasoline in the western United States. Equilon Enterprises (Equilon) was established as the company overseeing the joint operation. Equilon’s board of directors consisted of representatives from both Texaco and Shell, and Texaco and Shell each agreed to pool their resources and share in the profits and losses of Equilon’s business activities. Equilon sold gasoline under both the Texaco and Shell brands and set a single price for each brand. Shortly after the joint venture began, a class composed of the owners of Texaco and Shell service stations, represented by Dagher (plaintiff), brought a complaint against Texaco and Shell, alleging that Equilon’s price-setting practice was a price-fixing agreement and thus per se unlawful under § 1 of the Sherman Act. The district court granted Texaco and Shell’s motion for summary judgment, finding that application of the per se rule was not appropriate. Dagher appealed, and the court of appeals reversed the decision. Texaco and Shell appealed.