New York City's health care system, one of the finest in the world, is in a period of intensive turmoil. A growing proportion of uninsured residents is straining the system's capacity to provide access to care for everyone; in addition, more than a million uninsured families face dire financial consequences should one of their members become seriously ill or injured. Conversion of the city's Medicaid program, one of the nation's largest and most generous, from voluntary to mandatory managed care enrollment offers opportunities to improve care, yet also potentially jeopardizes the quality and accessibility of medical services for low-income residents. In combination, the rising number of uninsured New Yorkers and the shift to Medicaid managed care presents substantial challenges to the city's extensive network of safety net providers, including the Health and Hospitals Corporation, the world's largest public hospital system; academic health centers (AHCs); and community-based health clinics (CHCs).