BACKGROUND: There is widespread agreement among pediatric educators that continuity (following a panel of patients on a first contact basis for all their health care) is an important part of the education of pediatricians. OBJECTIVE: To measure continuity in a pediatric residency practice and to compare this continuity with 2 nearby private general pediatric group practices. We also examined measures of continuity suggested in the literature. DESIGN: Visit data were obtained from the practice billing system for a resident continuity practice and 2 nearby private practices for the 3-year period from July 1, 1992, to June 30, 1995. Visit data used were restricted to patients seen in the office of the practices during regular office hours. Continuity was measured using 5 different indices: 1) the usual provider of care index, visits by the usual clinician/total visits, 2) continuity for patient, the average proportion of visits that an individual patient was seen by his or her own physician, 3) continuity for physician (PHY), the average proportion of visits that an individual physician saw his or her own patients, 4) Continuity of Care Index (COC), and 5) the Modified, Modified Continuity Index. During the period examined, pediatric residents were present in the continuity practice for 1 half-day each week. The resident continuity practice (RCP) had 57 residents and saw 3386 patients for 18 955 visits. Private practice 1 (PP1) had 4 pediatricians who saw 4968 patients for 33 537 visits. Private practice 2 (PP2) had 5 pediatricians who saw 11 953 patients for 75 778 visits. RESULTS: For all visit types, continuity in the RCP was not as high as in the private practices, PHY-RCP versus PP1, PP2; 53% versus 70%, 77%. However, continuity in RCP was greater than 50% for all measures except the COC index, which precipitously decreases as the number of clinicians seen increases. Examining continuity for health maintenance visits (PHY-RCP, PP2 vs PP1; 96%, 96% vs 82%) RCP was equal to the best of the private practices. The percentage of patients not seen for a health maintenance visit during the study period was lowest in the resident practice (RCP/PP1/PP2, 15/22/30). CONCLUSIONS: Although continuity for all visits in this RCP was less than in private practice, it was surprisingly high, considering the limited time residents spend in clinic. In a particularly important area for continuity, health maintenance visits, continuity was identical to one and superior to the other private practice.