Medicaid is rapidly moving toward managed care throughout the United States and will have a major impact on care programs for those infected with human immunodeficiency virus (HIV). The experience at the Johns Hopkins HIV Care Service is an example of the transition from fee-for-service to managed care. The Maryland Medicaid program, which has required enrollment of all Medicaid recipients since June 1997, uses an adjusted payment rate and separately funds protease inhibitors. Elements that made the transition to a managed care organization possible included the early development of a comprehensive network of services and a database showing that historical Medicaid payments were low compared with the statewide experience. Our Medicaid managed care program promotes unlimited access to specialists, rejects the "gatekeeper" concept for any service, and includes an open formulary. Nevertheless, it is uncertain that the services now provided can be sustained with anticipated reductions in payments that seem inevitable with Medicaid policies here and nationally.