The 10 programs became operational between July 1998 and December 1999 and have encompassed all levels of security classification; they provided treatment services to both male and female felon inmates (5 male programs with 933 beds and 5 female programs with 1,102 beds). Inmates who were paroled from these prison-based TC treatment programs had the option of participating in up to 6 months of continued treatment in the community after release. Four regionally based Substance Abuse Services Coordinating Agencies under contract with the Department of Corrections provided transitional and case-management services to these parolees, regardless of whether or not they chose to enter aftercare. The evaluation study used a single group design to examine possible predictors of participation in aftercare and 12-month return-to-custody (RTC) among parolees who participated in prison-based TC substance abuse treatment. Primary statistical analyses consisted of logistic regression. Other statistical analyses were conducted post hoc to assist in the interpretation of the results of the logistic regression analyses. The findings are consistent with earlier similar studies in showing that increased time spent in prison TC's and aftercare were related to decreases in recidivism. Increased time in prison-based treatment predicted increased participation in aftercare, and subjects who participated in aftercare in urban counties spent longer periods of time in treatment than those in suburban or rural counties. A higher level of education was an important factor in delaying or preventing reincarceration. Regarding ethnicity as a factor in aftercare participation, the study found that Hispanic parolees successfully relied more on social and/or familial support systems than on aftercare programming. 3 tables, 4 notes, and 27 references