The health care delivery system in the United States is in transition. Increasingly managed care plans are gaining in predominance. The proliferation of managed care systems will have an impact on the demand and requirements for physicians. This paper attempts to project and estimate requirements for physicians in 2000 and 2020, assuming that the health care system will continue to be dominated by managed care. The projections are then compared to forecasts of physician supply under two separate physician production scenarios. The authors discuss the adequacy of the future physician workforce to provide services required by a health care system dominated by managed care.