The coexistence of psychiatric and substance abuse problems within the same patient occurs with significant frequency. These patients present serious challenges to a health care system which has traditionally treated mental health and substance abuse in separate venues, with differing and sometimes contradictory treatment modalities. Few studies exist on the treatment of the“dual diagnosis”patient utilizing an integrated approach, where both problems are addressed by the same staff on a single inpatient ward. We describe such a program in which dual diagnosis patients on one ward are separated into two different treatment tracks based upon the severity of their psychiatric illness. Follow-up measures at 3 months after discharge are compared for patients from each treatment track, with no significant difference found for the five outcome variables studied. This suggests that chronically mentally ill inpatients may benefit from integration of attention to their substance abuse problems with psychiatric treatment.