Effects of changes in a pediatric practice--expansion of the number of pediatricians and incorporation into a university hospital setting--on continuity of care and utilization were examined by means of a longitudinal study of a sample of 63 families. Continuity of care was measured by the following index: the number of visits with own physician divided by the total number of pediatric visits per year. Although continuity of well-child visits remained unchanged at the university setting, the continuity of sick visits declined markedly. An increased use of doctor visits for illness care was observed; its relationship with the decline in continuity is analyzed and discussed. While continuity is inherent in a small partnership practice, it is not so in a larger medical organization, particularly when involvement in patient care is part time. In such an organization, deliberate arrangements that enable patients with acute needs to receive care from their own doctors are needed.