The current ambulatory training of medical residents in the primary care program and the traditional program of the Massachusetts General Hospital, Boston, are described. All residents are assigned to work in a single medical group practice unit during their three years of training. Block outpatient rotations make up 32% of the primary care program and 6% of the traditional program schedules, while total ambulatory experiences, including weekly continuity sessions, make up 39% and 15%, respectively. Several components are important for a successful program. Above all is a vigorous group practice providing a sizable panel of patients with complex clinical problems from which residents can learn. Also important are financial support from the hospital and government or private grants and a commitment to outpatient teaching by the medical and nonmedical specialty staff.