There is concern that children with chronic conditions are less likely to be enrolled in managed care systems and that they may not receive optimal care. We studied the relationship between enrollment in an Independent Practice Association (IPA) plan and utilization of ambulatory services among children in a suburban pediatric practice with one mild chronic condition--those receiving hyposensitization therapy for allergic diseases. Ambulatory utilization by IPA patients (N = 102) was determined by medical chart review for one year before and one year after each patient switched from Blue Cross to IPA coverage. Blue Cross hyposensitization patients (N = 57) matched for age served as controls. Patients receiving hyposensitization were more likely to have enrolled in an IPA than those not receiving hyposensitization (70% vs 45%, p < .001). Before enrollment pre-IPA patients had 41% fewer well-child care (WCC) visits than Blue Cross patients (p < .01); both underutilized WCC visits according to established guidelines. Controlling for age and baseline utilization, we found a significant increase in WCC and acute care visits after IPA enrollment (p < .05), but no change in hyposensitization visits or referrals. In this setting, there was no evidence for reduced access to ambulatory services but rather evidence for improved utilization of primary care.