American civil litigation is adversarial — both in the sense of fitting within the adversarial tradition of party-driven litigation followed in most common-law countries, and in the sense of being aggressively combative. Yet within U.S. civil litigation is an undercurrent of cooperativism. This article uncovers cooperativism in the procedural rules and common party practice, and it situates cooperativism within both adversarialism and judicial managerialism. The article argues that cooperativism is a story in its own right, one that should not be overlooked.