Will primary care practices set up by physicians trained in combined internal medicine-pediatrics residencies be successful? To address this question, the recruitment of patients to the medicine-pediatrics office established in May 1985 by a northeastern medical center and the patients' understanding of and satisfaction with the combined practice were studied via the billing system and a questionnaire mailed to 1,001 households of patients in November 1988. Although equally divided between children and adults, the patient population had two large bulges, infants less than 2 years old and young adults aged 18-39 years. Most of the 833 patients (from 406 households) who returned the questionnaires were well educated and professional. They indicated they were aware of the nature of the practice; had been looking for a specialist, not a "doctor for the family"; and were highly satisfied. Therefore, the medicine-pediatrics residency program studied appears to have been very successful in preparing primary care physicians. These physicians had a particular appeal to young upper-middle-class families.