Primary care tracks in internal medicine residency programs were initiated in the late 1970s in response to the need for more primary care physicians. These programs have shown that internists can be trained effectively in ambulatory settings. Graduates of primary care tracks are more likely to choose careers in general internal medicine than are other internal medicine graduates. Primary care internist training has been accompanied by the growth of academic general internal medicine divisions and by the enhancement of the scientific base for ambulatory care practice and medical education. Expanded ambulatory training opportunities, modeled after current primary care tracks, should be offered to all residents in internal medicine. At the same time, primary care tracks should be revised to address deficiencies in current ambulatory training. These tracks should be designed to commit most resident time to ambulatory care settings, to involve residents in community-based and interdisciplinary health care, and to expose residents to conditions outside of the medical sector that affect health. Revised primary care tracks can serve as pathfinder programs for ongoing reform in internal medicine residency training. Three models for organizing and funding such reform are presented.