This article presents findings from an exploratory study of three programs using the Housing First approach to provide permanent supportive housing for single, homeless adults with serious mental illness and often co-occurring substance-related disorders. This approach provides direct, or nearly direct, access to housing that is intended to be permanent without requiring sobriety or psychiatric treatment. Findings from the three programs examined for this study indicate that the Housing First approach may help the hardest-to-serve chronically homeless population achieve housing stability. Of the 80 participants tracked over 12 months, 84% remained enrolled in the Housing First program for 1 year following program entry. One half of those spent every night in their Housing First unit, while the others spent some time in other living environments. (Contains 5 tables.)