This data collection consists of a process and outcome evaluation of the Ozark Correctional Center Drug Treatment Program (OCCDTP), located in an all-male, 650-bed minimum security prison. For the process evaluation, the principal investigators evaluated changes in OCCDTP treatment activities, characteristics of OCCDTP participants, utilization of aftercare, and participant ratings of the program and aftercare. For the outcome evaluation the researchers compared how well program graduates fared after program completion with respect to relapse and recidivism compared to program dropouts, as well as to a comparison group of inmates who did not participate in the OCCDTP. Data were collected from the Missouri Department of Corrections, the Missouri State Highway Patrol, a psychosocial assessment of clients entering the OCCDPT program, and three-month and 12-month follow-up surveys. Variables include background and demographic information, such as race, marital status, religious preference, and education level, as well as information on mental health, substance abuse, criminal history, nature of offenses, recidivism, clients' perceptions of the program, participation in aftercare, and social and clinical data.