Book excerpt: Chronic homelessness is a highly complex social problem of national importance. The problem has elicited a variety of societal and public policy responses over the years, concomitant with fluctuations in the economy and changes in the demographics of and attitudes toward poor and disenfranchised citizens. In recent decades, federal agencies, nonprofit organizations, and the philanthropic community have worked hard to develop and implement programs to solve the challenges of homelessness, and progress has been made. However, much more remains to be done. Importantly, the results of various efforts, and especially the efforts to reduce homelessness among veterans in recent years, have shown that the problem of homelessness can be successfully addressed. Although a number of programs have been developed to meet the needs of persons experiencing homelessness, this report focuses on one particular type of intervention: permanent supportive housing (PSH). Permanent Supportive Housing focuses on the impact of PSH on health care outcomes and its cost-effectiveness. The report also addresses policy and program barriers that affect the ability to bring the PSH and other housing models to scale to address housing and health care needs.