To assess the efficacy of an interpersonal process-oriented and cognitive-behavioral group psychotherapy program, 36 incarcerated male adults were assigned to either a treatment group (n = 20) or a no treatment control group (n = 16). Outcome measures consisted of paper-pencil self-report instruments, institutional behavioral data, and structured interviews with the group therapists (n = 3). 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.