Research has shown that substance abuse treatment is associated with reduced criminal activity as well as reduced drug use. An increasingly important aspect of treatment evaluation, however, is understanding more about the therapeutic process involved. Based on a sample of 279 probationers assigned to residential treatment for drug use problems, the purpose of this study is to examine several elements of treatment process and how they influence recidivism. Rearrest rate during a 2-year follow-up study period was 36%, and survival analysis showed it was directly related to poorer during-treatment ratings by probationers of self-esteem, counselor competence, and peer support from others in the treatment program. These were better predictor measures than background and demographic characteristics generally used in other studies, suggesting the role of therapeutic engagement in the recovery process.