This is the first report in the Urban Institutes evaluation of the Special Homeless Initiative (HI), state funding to the Massachusetts Department of Mental Health that is used to prevent or end the homelessness of people with serious mental illness who are or are eligible to become DMH clients. The report covers the history of the HI, its public policy principles, and the larger context of DMH programs and policies into which the HI fits. It describes how DMH staff use the HI in negotiation with housing developers and homeless service providers to expand the supply of permanent supportive housing, the array of housing made available through the HI and the other types of housing that DMH offers, as well as use of HI funds to provide specialized services such as supports for substance abuse recovery and employment.