Prologue: Almost two decades ago, the Carnegie Commission on Higher Education declared in a report, “The most serious shortages of professional personnel in any occupation group in the United States are in health services.” In the ensuing years, Congress sharply increased the federal investment in health professional education and, as a result, bolstered the total supply of providers in a spectacular fashion. Now, the conventional wisdom holds that the United States has more physicians than it can afford to support. In this paper, Steven Jacobsen and Alfred Rimm challenge this view held by the Reagan administration and, increasingly, by the American Medical Association (AMA). A Commentary in this issue by Ruth Hanft also questions the notion that America has a physician surplus, to which the leaders of the AMA and the Association of American Medical Colleges (AAMC) respond. Here Jacobsen and Rimm reassess the supply predictions of the Graduate Medical Education National Advisory Committee (GMENAC), adjusting them for changing practice patterns, growing numbers of women entering medical training and practice, new medical school enrollment trends, and number of foreign graduates that continue to enter residency in this country. Their results differ greatly from GMENAC's predictions. Jacobsen, a student of biostatistics and medicine at the Medical College of Wisconsin, is currently pursuing doctoral studies in epidemiology at the University of Illinois in Chicago. Rimm, also of the Medical College of Wisconsin, is a biostatistician and an epidemiologist certified by the American College of Epidemiologists. He holds a doctorate in agriculture and quantitative genetics from Rutgers University, and his background encompasses a wide variety of epidemiological studies, including chemotherapeutic clinical trials at the Roswell Park Cancer Memorial Institute in Buffalo, New York during the 1960s. Currently he is serving on a Health Care Financing Administration committee whose purpose is to rank 5,700 hospitals in the U.S. by quality of care. The research upon which this article is based received the Thomas Hale Ham award from the AAMC in October 1986.