There are significant knowledge gaps concerning the experiences of families of persons with co-occurring substance and mental disorders and the impact of families on treatment of individuals with these disorders. This paper presents a conceptual framework for examining family involvement of adults in treatment for co-occurring substance and mental disorders. An overview of the characteristics, problems, and needs of these individuals and their family members is presented. The extant literature pertaining to our conceptual framework is reviewed with focus on predictors of family involvement with clients, predictors of family member involvement in clients' treatment, and consequences of family involvement for client treatment outcomes. Gaps in the research literature and implications for future research and practice are discussed.