The generation of medical students now being taught will be practicing into the middle of the next century. They will be expected to provide an expanding array of clinical preventive services and be responsible for the health and well-being of entire populations and communities. Although prevention principles are being taught in many contexts, most medical schools do not have adequate curriculum-tracking systems that allow them to track the delivery of education and training in disease prevention and health promotion. The Bureau of Health Professions of the Health Resources and Services Administration (HRSA) and the Association of Teachers of Preventive Medicine have worked on several projects that have culminated in the development of a set of core competencies in preventive medicine for undergraduate medical education. In 1997 they convened a task force of medical educators from a broad array of basic science and clinical disciplines representing major U.S. medical teaching societies. The task force reviewed and updated the 1984 Inventory of Knowledge and Skills Relating to Disease Prevention and Health Promotion so that it would be relevant to faculty in diverse specialty areas and could be integrated throughout the medical curriculum. They then created a list of competencies that are essential from the perspective of each discipline and all disciplines. The article gives the context for teaching preventive medicine, presents the core competencies, and serves as the introduction to a supplement to Academic Medicine on teaching preventive medicine throughout the undergraduate medical curriculum.