Internists - "doctors for adults" - provide most of the medical care given to older Americans, especially those with serious chronic disease. Nonetheless, the United States lacks an adequate physician workforce with mastery in caring for older persons and with expertise in building knowledge about how best to provide this care. This supplement aims to strengthen the physician workforce by fostering incremental and sustained improvements in the training of internal medicine residents in the care of older adults and in the development of geriatrics-oriented general internal medicine faculty. It identifies 3 major barriers to these improvements: lack of adequately trained teachers and mentors, the belief that explicit training in geriatrics has little to offer the generalist, and inadequate funding. Three strategies offer particular promise in overcoming these barriers: engaging directors of internal medicine residency programs, funding centers to promote collaboration between teaching and research programs in general internal medicine and geriatrics, and providing substantial incremental funding on the national level to pay for the time required to care for frail older patients and to teach and do research about this care. The barriers and strategies identified in this supplement may also inform efforts to enhance the skills of practicing physicians and improve training and faculty development in family medicine and other disciplines.