In this article, we analyze how pluralistic, competitive, and conflictual interest group amicus curiae participation is in the U.S. Supreme Court. Examining participating organizations and briefs during the 1995 term, we address three inquiries. First, we scrutinize the types of organized interests who participate as amici curiae. We find that the Court is open to a wide array of interests and that particular types of groups do not dominate amicus activity. Second, we analyze the frequency with which amici file briefs on opposing sides of dispute. We reveal few strict patterns of competition, suggesting that Supreme Court cases are salient to a diverse spectrum of interest groups, many of which are not usually thought of as being in competition with one another. Third, we investigate how often and which amici directly cite one another for purposes of invalidating each other's argumentation. While amici have a great deal of opportunity for this form of direct conflict, it is surprisingly rare. Nonetheless, when amici engage in this express form of discord, they play a clear role in shaping the flow of information at the Court.