Several major waves of prison riots in the 20th century are identified. The first wave coincided with World War I; the second wave, which began in 1929 and lasted for about 2 years, coincided with the introduction of 'new criminology', which advocated the rehabilitation made; the third wave coincided with the Korean War. The decline in prison riots from 1953 till 1968 is noted, followed by a recounting of the bloodiest riot wave in prison history, culminating in the riot at Attica State Prison (New York). Reasons for riots, including overcrodwing, poor food, and inhumane prison administration, are analyzed, as are the social organizational characteristics of prisons. The prison is analyzed as a solidary-opposition social system and as a mixed-goal institution of treatment and custody. Additionally, the racial, political, and ideological tensions in prisons are considered, and the relative deprivation thesis is explored. Reasons for the Michigan riots are identified; the presence of anomie (absence of definitive norms and sense of purpose that leaves a power vaccuum) in the prison system is suggested. The movement of the Michigan system toward anomie is traced to the mid-1970's. Ways to minimize prison riots are suggested, including the use of effective inmate grievance mechanisms, the use of inmate councils as channels of communication between inmates and prison officials, the use of an inmate inventory to enable inmates to communicate their concerns nonverbally, and staff training in the recognition of inmate unrest. Attention also focuses on the need to minimize prisoners' and outsiders' discontent. Thirty-five references are listed.