Individuals disabled by both mental illness and chemical abuse, often referred to as dually diagnosed or disordered, provide unique and perplexing problems for treatment providers. The development of a treatment program that evolved from a traditional community based psychosocial day treatment modality to an outpatient rehabilitation program which utilizes multidisciplinary clinical approaches is discussed in detail. Staffing issues, as well as roles of the treatment team and client group members, are presented. Systems adjustments are discussed in relation to the ongoing development of a model treatment program that provides services to clients with severe psychosocial deficits, as well as substance abuse problems.