Studies have shown that interest groups can and often do use litigation to advance their goals. However, the literature has not specifically examined how significant changes in the law affect this behavior. A longitudinal research design allows this question to be addressed, and obscenity provides an excellent case study. In Miller v. California (1973), the Burger Court reversed the Warren Court's liberalization of obscenity law. The reversal stimulated a shift in the litigation burden among the thirteen libertarian groups involved in this litigation: groups moved by material interests mobilized to become the preeminent litigators, filling the void created by the exit of the more politically motivated ACLU. However, the reaction of material groups was not uniform: commercial groups litigated narrow questions with narrow arguments, while professional organizations engaged a broader range of issues and made arguments closer to those previously tendered by the ACLU. These diverse responses were conditioned by internal (group type, intensity of commitment, nature of goals) and external (disposition of courts, nature of threat, presence of other groups) factors. In addition to demonstrating the dynamics and vastness of the group litigation system, this research suggests the utility of a group theory perspective in developing a more generalized approach to the study of group litigation.