Context: More than 350 communities in the United States have committed to ending chronic homelessness. One nationally prominent approach, Housing First, offers early access to permanent housing without requiring completion of treatment or, for clients with addiction, proof of sobriety. Methods: This article reviews studies of Housing First and more traditional rehabilitative (e.g., "linear") recovery interventions, focusing on the outcomes obtained by both approaches for homeless individuals with addictive disorders. Findings: According to reviews of comparative trials and case series reports, Housing First reports document excellent housing retention, despite the limited amount of data pertaining to homeless clients with active and severe addiction. Several linear programs cite reductions in addiction severity but have shortcomings in long-term housing success and retention. Conclusions: This article suggests that the current research data are not sufficient to identify an optimal housing and rehabilitation approach for an important homeless subgroup. The research regarding Housing First and linear approaches can be strengthened in several ways, and policymakers should be cautious about generalizing the results of available Housing First studies to persons with active addiction when they enter housing programs. © 2009 Milbank Memorial Fund.