This paper examines outcomes 12 months post-prison release for offenders with co-occurring disorders (n = 185) randomly assigned to either a mental health control treatment (C) or a modified therapeutic community (E). Significant between-group differences were not found for mental health measures, although improvements were observed for each group. Reductions in criminal behavior were associated more with substance use than improvements in mental health symptoms, supporting the primacy of substance abuse treatment in affecting recidivism. Additional study of this population is needed to describe the relationships among diagnostic subgroups, as well as change in substance use and in mental health symptoms. (Contains 4 tables and 2 notes.)