Objective: This study measured the impact of an assertive case management program for psychiatrically disabled homeless persons in metropolitan Toronto. It was hypothesized that the program would improve residential stability, reduce psychiatric symptoms, improve social functioning, improve social networks, and increase use of appropriate services. Method For 59 clients admitted to the program, assessments for the nine-month period before program entry were completed and were repeated nine months later. The Brief Psychiatric Rating Scale and a version of the Scale for Level of Functioning were the main measures of outcome. Results: At follow-up significant improvements in residential stability and reductions in psychopathology were demonstrated. Improvements in social functioning and increases in social network size were significant. Although no baseline data about service use were collected, clients used basic support services during their first nine months in the program. Conclusions: The success of the program demonstrates that a difficult-to-treat patient population can be helped in a humane fashion if trained personnel are available.