The Mid-America Institute on Poverty of Heartland Alliance was hired by the Supportive Housing Providers Association to study the impact of supportive housing on use of publicly funded services. In particular, the study focuses on the change in service use and the cost of services used by Illinois supportive housing residents 2 years before entering supportive housing and 2 years after. This study will inform policymakers, funders, and others about the importance and cost effectiveness of supportive housing in Illinois. The study began in January 2005 and will end with a final report in December 2008. This snapshot is the first report released on the study, analyzing data collected from residents at the time of study enrollment.