Data sources were 1974 and 1979 national surveys of State prison inmates. The 1974 survey was based on a national sample of 1,670 male offenders last released from a State prison in 1970-74. The 1979 survey was based on a national sample of 934 male offenders last released from a State prison in 1975-79. The study focused on prison release cohorts and admission cohorts who had previously served time in a State prison. Recidivism patterns were described in terms of 'crime switch' matrices. Prior to conducting release and admission cohort studies, the relationship between prison time since admission and incarceration offense was analyzed. The release cohort analysis compared recidivism patterns of 1974 and 1979 prison inmates whose last prison release had not been more than 5 years prior to the survey time. The analysis determined there was a strong, statistically significant relationship between the natures of the prior and current incarceration offenses. For violent and property offenses, there was higher than a 50-percent probability of repeat occurrence. Other release-cohort findings pertained to the difference in the 'crime switch' matrix between the 1970-74 release cohort and the 1975-79 release cohort. The relationships between inmate race, age, and years released and the 'crime switch' matrix were examined as well. The study of admission cohorts focused on the types of offenders imprisoned during a given time period. Tabular data and 27 references.