The study focused on male prison inmates aged 17-54 at the time of sentencing who were released from the State Prison of Southern Michigan, the Michigan Training Unit, and the Michigan Reformatory from January 1969 through December 1973. A total of 4,379 men with five types of releases were identified. The educational files of these men were reviewed to determine which ones has been enrolled in vocational programs. The trainee group was finally reduced to 386. The sample selection procedure next required the matching of the selected trainee group to a control group so that the observed differences in recidivism after release would reflect primarily the experiences of vocational training. The recidivism patterns of the sample were followed through December 1974. Recidivism was defined as reincarceration in a Michigan State prison due to a new sentence or parole violation after the first release within the period 1969-73. Findings show that the professional vocational training programs, consisting of computer programming, data processing, electronics, machine drafting, and vocational music, consistently demonstrated a favorable impact on the trainees. The professional programs, accounting for about 61 percent of the trainees, significantly reduced the probability of recidivism. The craftsmen, clerical, operatives, and service worker training, however, consistently failed to demonstrate favorable impact on the trainees in reducing the probability of recidivism. Tabular data and 19 references are provided.