Medical education will change from within in response to continued advances in biological sciences and technology, but changes that are occurring outside the natural sciences can have greater impact, especially (1) the reconceptualization of the meaning of health, (2) the increase in the number and range of different health improvement strategies, (3) the growing awareness of the paradox of the relatively low health status of the U.S. population and high per-capita and national health care expenditures, and (4) shifts in the causes of illness and death. These changes make it necessary for medical students to be given a foundation in both the natural and the social sciences, for most ill health has causal roots in both the social and physical environment, even though it is not understood how some of these outside influences are translated into disease or biologic derangements that lead to disease. Consideration should be given to changes in medical education that include (1) interpreting the sociology as well as the biology of health, (2) expanding the horizons of medicine to incorporate health improvement as well as disease cure, (3) training for population-based health care at the community level, and (4) learning to assess medical outcomes with more than biometric measures to include measurements of functioning and well-being. The author presents in detail a health input-output model to show the complex interrelationships of socio-ecologic (i.e., outside) factors and the individual's genetic-biologic makeup (inside factors) that determine the individual's state of health.