School-based health centers have mushroomed as a source of care for children, especially those in the inner city. However, their effect on the health outcomes of children, particularly those with chronic illness, is poorly documented. This survey of 6400 parents of children in 6 inner city elementary schools found that, among children with asthma, the rate of hospitalization was 50% higher among children at schools without a health center. While there was no effect on emergency department utilization, children with asthma missed fewer days of school if they attended a school with a health center. These findings support the efficacy of school-based health centers for inner-city children with asthma and have implication for access to school-based primary care.