To assess the efficacy of an interpersonal process-oriented and cognitive-behavioral group psychotherapy program, 36 incarcerated male adults (mean age 32.2 yrs) were assigned to either a treatment group or a no treatment control group. Outcome measures consisted of paper-pencil self-report instruments, institutional behavioral data, and structured interviews with the group therapists. Results indicated no significant changes in inmates' level of defensiveness, empathy, or institutional behavior; however, the inmates reported universally positive reactions to the treatment program. The group therapists also perceived the treatment program as efficacious, particularly in fostering a cohesive group atmosphere and increasing inmate responsibility for group leadership. Implications for practice and research are discussed. (PsycINFO Database Record (c) 2019 APA, all rights reserved)