Objective: This study investigated the sociocultural implications of group interactions of drug-addicted inpatients during two-year group psychotherapy. Methods: In a psychiatric ward especially designed to promote abstinence, all drug addicts were encouraged to participate in semi-structured, here-and-now focusing, task-oriented and reality-based group psychotherapy sessions. A heterogeneous group of 144 opiate, pentazocine, amphetamine and glue addicts received group psychotherapy from May 1990 to May 1991. and another homogeneous group composed of 117 amphetamine addicts received group psychotherapy from June 1991 to May 1992. Each treatment was conducted in an inpatient setting arid consisted of 72 twice weekly 90-minute open sessions. Results: Analysis of group interactions among inpatients revealed that active members sat closer to the therapist in the heterogeneous group; on the contrary, active members sat closer to the cotherapist in the homogeneous group. Because of more forensic issues in the heterogeneous group, members tended to show more hostile interactions toward the therapist and defensive relationship with others; whereas in the homogeneous group, members tended to show the interaction pattern of need for more support and approval through the therapist and experience sharing relationship with others. The main topics presented by the members were compatible with the actual life experiences in both groups. Attendance rates were lower in the homogeneous group due to the disturbing effects of psychotic symptoms. Conclusion: The findings of this study suggest that it would be possible to improve the effectiveness and outcomes of group psychotherapy for drug addicts through decriminalization of drug use, and careful screening of patients and by taking measures to prevent competition between the therapist and cotherapist during psychotherapy. We also suggest that implementation of a ward recovery group model followed by community self help after discharge may be the most effective management for drug addicted inpatients. (Full Text in Chinese)