The authors describe the development and evaluation of a primary care residency program encompassing both internal medicine and pediatrics. The combined residency is a four-year program of alternating six-month rotations in the two disciplines. One-fourth of the program is ambulatory medicine and includes training in a clinic for children and adults. Patient demographics are maintained for each resident, and an ambulatory-medicine-focused curriculum consisting of weekly conferences and self-directed independent study is used. The program is routinely evaluated and is highly rated by patients and residents. Factors critical to its success include emphasizing goals and experiences in outpatient versus inpatient care, developing an ambulatory practice to help support resident salaries, adequately preparing residents to take the board examinations in both disciplines, and providing a comprehensive primary care curriculum.