A physician shortage is likely given current levels of medical education and training. Because an increase in physician supply through expansion of U.S. medical school capacity will require ten or more years, there is little time left to affect the supply of new physicians in 2020 when a substantial number of baby boomers will be over 70 years of age. Even with a substantial increase in medical education and training capacity, it is unlikely that all of the increased demand for health services can be met with physicians. In addition to the challenges of expanding medical school enrollment, the nation will need to grapple with other ramifications of demand exceeding supply. This includes assessing how to deliver services more effectively and efficiently and the future roles of the physician and other health professionals. These challenges are particularly difficult for medical schools and teaching hospitals, the cornerstones of medical education and training in the United States. Osteopathic and off-shore schools targeted to Americans have been willing and able to grow more quickly and less expensively than U.S. medical schools, in part because of their more narrow approaches to medical education. In addition, physicians from less developed countries continue to migrate to the United States in significant numbers. Medical schools, teaching hospitals, and policymakers will need to address several major questions as they respond to the shortages. They will either confront and address these issues in the next few years or they will be forced to change by others in the future.