The provision of adequate housing for the severely mentally ill homeless has been considered a prerequisite for successful treatment. Whether or not providing access to independent housing environments without on-site support is an effective means for stabilizing this population in the community is far less studied. Preference studies indicate a strong desire for access to independent housing, but little is known about the ability of mentally ill homeless persons to remain in independent housing when such access is provided. The McKinney Homeless Research Demonstration Project in San Diego, CA evaluated the effectiveness of using Section 8 certificates as a means of providing independent housing to the severely mentally ill homeless. Three hundred sixty-two clients took part in a long-term experimental study employing a randomized factorial design. Clients were assigned to one of two types of supportive case management (comprehensive vs. traditional) and to one of two levels of access to independent housing (using Section 8 certificates). Innovative longitudinal summaries of housing outcomes were developed based on clients' patterns of living over time. Nine different patterns of living arrangements were identified, ranging from continuous occupation of independent housing to consistently unstable housing. Access to Section 8 housing markedly increased the probability of achieving stable independent living arrangements and of continued contact with case management services. A subset of clients in all experimental conditions followed less successful housing patterns, indicating the need to develop different service programs for individuals with different needs. Overall, however, access to independent housing had very positive effects on residential stability. © 1996 John Wiley & Sons, Inc.