Managing the health care workforce will have important implications for costs, quality, and access. Factors influencing supply include the production of new professionals, their relative effort, and rates of retirement. Demand will depend upon the development of new diseases, new drugs, and technologies, as well as the growth of managed care, which uses fewer physicians, fewer specialists, and more midlevel practitioners. There is a general consensus that there are too many physicians, especially specialists. Reducing the number of residency positions would reduce supply, predominantly by slowing importation of international physicians. Obstacles to workforce reform include a distrust of supply projections, skepticism about governmental planning, conservatism of established institutions, and the reality that some hospitals would lose positions and resources.