In March 1972 a private family practice in Hamilton, Canada, became a teaching practice of McMaster University. Subsequently a before-and-after study was conducted to compare characteristics of the patients and the impact of the change on the practice. There was a 34 percent reduction in practice size. There was a shift to younger patients and a substantial drop in mean patient income. Utilization rates of health services rose, particularly hospitalization, even though the average length of stay decreased. Profiles of complaints and diagnoses remained very similar. Quality of care scores were comparable with those of community controls before and after the change. Gross income from clinical earnings dropped, but the amounts per person per year were very similar in the two periods. It is concluded that the "transplanted private practice" which becomes part of a school of medicine is a realistic teaching resource in primary care.