Class action suits frequently have been used as a strategy for improving the quality of mental health care. Psychiatrists, psychologists, and professionals from related disciplines have been involved in these suits in different roles. This article presents and discusses case examples of these roles, which include the expert witness, court-appointed expert, consulting expert, monitor, special master, receiver, advocate, amicus curiae, plaintiff, and defendant. The authors caution against assuming dual roles and argue that professionals, before beginning to participate in this complex arena, should clarify their functional responsibilities, the legal basis of their involvement, and the ethics principles that will guide their actions.