The treatment of individuals with coexisting psychoactive substance abuse and severe psychiatric disorders requires an integration of principles from the mental health and chemical dependency fields. The authors outline a conceptual model for treating dually diagnosed patients that consists of four treatment phases—engagement, persuasion, active (or primary) treatment, and relapse prevention. The components of these phases include case management, group therapy, psychopharmacology, toxicologic screening, detoxification, family involvement, and participation in self-help groups. Due to the high morbidity and mortality associated with dual daignoses, the authors encourage the development, implementation, and scientific evaluation of integrated treatment models targeted toward this population.Abstract Teaser