Eliminating health disparities will be difficult as long as many rural and disadvantaged inner-city communities remain medically underserved. The authors argue that the current debate on physician workforce policy has not adequately emphasized medical schools' social mission to educate physicians who will improve health care access and equity; fulfilling that mission means training students who will deliver primary care to underserved people. But fewer medical students are entering primary care specialties and practicing in underserved areas, and students who have the characteristics that make them likely to select such careers are increasingly uncommon among medical school matriculants. Unless there is a dramatic change, the imbalance will only become worse. The authors argue that the epidemiology of medical student career choice is sufficiently understood to permit schools to accept applicants with those characteristics, both demographic and individual, that are known to increase the probability of students caring for populations in need after graduation. Programs that have selected students on the basis of those predictors have been successful in increasing the distribution of doctors to primary care specialties and underserved areas, but these have not been of sufficient scope. The authors present a proposal for prioritizing medical school admissions to favor applicants who, rather than delivering just high grades, will contribute to improving America's health care outcomes.