Widespread recognition of the problem of dual disorders, defined here as coexisting substance use disorder (substance abuse or substance dependence) and severe mental illness, has led to the development of programs that integrate mental health and substance abuse treatments. In this article, the authors provide a brief summary of problems related to traditional treatment approaches for persons with dual disorders. They then define integrated dual-disorders treatment and describe common components of these programs: assertive outreach, comprehensiveness, long-term perspective, shared decision making, stage-wise treatment, and pharmacotherapy. The authors elaborate on the concept of stages of treatment (engagement, persuasion, active treatment, relapse prevention), including the specific goals of each stage, and provide examples of clinical interventions for achieving designated goals. Research on integrated treatment is then briefly summarized. The article concludes with a discussion of future directions for work in this area.