This article examines the nexus between modern psychological theory (especially contextual or situational models of behavior), contemporary prison policy, and the legal concept of cruel and unusual punishment. It briefly reviews the history of imprisonment in the United States and the role of psychology in the development of prison punishment. An analysis of research on the psychological effects of imprisonment is presented, followed by a discussion of contemporary 8th Amendment law. Finally, modern psychological theory is used as the basis for a series of proposed correctional and legal reforms.