Although the links between health and environment are well known, interventions that target these associations in order to improve health are rare. Health and social service agencies often function independently of one another, maintaining separate, unlinked databases. For example, relationships among homelessness, AIDS, and tuberculosis have been noted, but services have not focused on the intersecting populations these conditions affect. This Issue Brief summarizes efforts to merge databases and provide policymakers with information to guide housing, social service, and health care resources. The investigators identify risk factors associated with AIDS among the homeless, and homelessness among people with AIDS.