No special needs group among people with mental retardation and developmental disabilities strains the service capacity of community and residential services to a greater extent than do people with dual diagnoses of developmental and psychiatric conditions. During the past decade many provider agencies have developed specialized services for people with dual diagnosis. Some have specialized in a primary focus of service for such people, including residential or housing and day services. Although these programs incorporate mental health services and heightened clinician presence and influence on everyday activities compared to other developmental services programs, progressive specialized programs also include key elements typical of the most progressive nonspecialized settings. The program models for residential and day services in this book include the entire range of residential and housing options available for people with dual diagnosis. These program models share common features that are responsive to the prevailing philosophy of individualized service, tempered by important differences in service mix and approaches that reflect differing needs of different subgroups of people with dual diagnosis.