In 2014, most homeless people will become Medicaid-eligible under the Affordable Care Act (ACA) of 2010 based on their low incomes. Many homeless people have complex physical and behavioral health conditions for which they seek care through frequent use of emergency rooms and inpatient hospitalization, at considerable cost in public resources. With appropriate supportive services, inappropriate use of crisis health services can be avoided. Medicaid reimbursement is an important source of funding for many of the health, care coordination, and recovery support services that help homeless people succeed in housing and stop such inappropriate use. Among the best indicators of Medicaid’s potential usefulness to homeless people once they become beneficiaries are the ways that today’s providers have been able to use Medicaid to cover health care and behavioral health care for people who have been chronically homeless and are now living in permanent supportive housing (PSH). In October 2010, the U.S. Department of Health and Human Services (HHS), Office of the Assistant Secretary for Planning and Evaluation, contracted with Abt Associates Inc. for a study to explore the roles that Medicaid, Community Health Centers, and other HHS programs might play in providing services linked to housing for people who experience chronic homelessness through PSH. Permanent Supportive Housing provides a permanent home for formerly homeless people with disabilities, along with the health care and other supportive services needed to help tenants adjust to living in housing and make the changes in their lives that will help them keep their housing. It differs from group homes, board and care facilities, and other treatment programs in that most tenants hold their own leases, and keeping their housing is usually not contingent on their participating in services or remaining at a certain level of illness. Because Medicaid is implemented through partnerships between states and the Federal Government, every state’s Medicaid program is different. Medicaid is only one component of strategies that communities use to create and sustain supportive housing. It does not pay for housing costs, and Medicaid reimbursement is available only for services that address health-related issues. This study focuses on communities known to be using Medicaid to provide integrated health, mental health, and substance use services combined with housing for chronically homeless people. Other states and providers will develop new models of service delivery and reimbursement in the coming years.