This Treatment Improvement Protocol (TIP) presents an overview of the role and efficacy of group therapy in substance abuse treatment. TIPs are best-practice guidelines for the treatment of substance use disorders that make the latest research in substance abuse treatment available to counselors and educators. The content was generated by a panel of experts in the fields of group therapy and substance abuse treatment, and reviewed by independent experts. The seven chapters offer a theoretical basis for the effectiveness of group therapy, and describe the purpose, main characteristics, leadership and techniques of different types of group therapies. Criteria for matching a client to a particular group, ways to prepare a client for participation in a group, as well as the client's stages of treatment and recovery are also considered. Fixed and revolving types of therapy groups, and the variables of effective group leadership are explored, and confidentiality regulations concerning alcohol and drug treatment in group treatment settings are discussed. In the final chapter, supervisory issues and training opportunities for substance abuse professionals are highlighted. Appended are: (1) Bibliography; (2) Adult Patient Placement Criteria; (3) Sample Group Agreement; (4) Glossary; (5) Association for Specialists in Group Work Best Practice Guidelines; (6) Resource Panel; (7) Cultural Competency and Diversity Network Participants; and (8) Field Reviewers. The appendices are followed by an Index, and CSAT TIPs and Publications. (Contains 7 figures.)