This study identifies trends that will lead to a dramatic increase in the number of active physicians in the United States during the next decade. The supply of active medical doctors (MDs) and doctors of osteopathy (DOs) as well as active post-graduate MDs and DOs in the U.S. is projected to increase by approximately 50 percent in the decade ending in 1985. The number of active physicians per 100,000 population is similarly expected to increase by approximately one-third. The production of surgical specialists, in particular, appears to be excessive. In response, the average length of physician graduate training programs is anticipated to be shortened as more MD and DO graduates enter shorter, general practice residencies. The authors expect that the effects of this projected increase in the supply of physicians may relieve geographic disparities in physician distribution, rationalize the organization of medical practice, and reduce physicians' incomes relative to other professional groups and possibly in absolute terms. The projected increases in the supply of physicians will give the federal government much more flexibility and bargaining power should it choose to implement a national health insurance program with salaried physicians.