In recent decades the community mental health movement has achieved a dramatic reduction in the census of state and county mental hospitals in the United States, and hundreds of federally-funded community mental health centers have been established nationwide. At the same time, national controversy has arisen in response to what in places has seemed the haphazard process of implementing "deinstitutionalization" and the fate of many chronically mentally ill persons who are without needed social services and psychological care. Despite the widespread attention that this contemporary program has received, theoretical analysis of the complex social, scientific, intellectual, and political origins of America's community mental health policy remains deficient. This article examines the background and development of the Community Mental Health Centers Act of 1963, tracing how an important shift in national policy toward the mentally ill grew out of changing perceptions--among policymakers, professional groups, and the general citizenry in the post-World War II era--of the nature of the problem of mental illness.