The My Lai massacre, Watergate, and the Iran-contra affair are examples of the tendency for people to commit illegal acts when ordered by authority and for others to excuse such acts as not subject to ordinary morality. The authors present a detailed description of the My Lai massacre and the trial of Lieutenant William Calley. They explore historical and contemporary concepts of authority, focusing on the duty to obey and the duty to disobey in the context of religious traditions and military law. A social-psychological framework is constructed for analyzing the structure and dynamics of authority and for assigning responsibility in authority situations. The analysis highlights obstacles to challenging authority and conditions under which obstacles can be overcome. The results of two surveys conducted to assess public opinion of the Calley trial, Watergate, and similar events show that people's position on the issue of crimes of obedience depended on their stand regarding authority and responsibility. Many felt it was the subordinate's duty to obey orders, while others felt that orders must be assessed against individual values and that acts should be judged by ordinary moral criteria. Three broad orientations to political authority are identified that focus on rules, roles, and values. Ways citizens can be encouraged to resist authority when orders violate fundamental moral principles are suggested. Supplemental information on the Calley trial and public opinion surveys is appended. 383 references, 30 tables, 2 figures.