Health-care expenses for children with special health-care needs (CHSCN) can be large and unpredictable. The purpose of this study was to investigate the medical expenditures for CSHCN. A retrospective analysis was conducted of paid claims from multiple billing and payment sources for 1,130 children served at a regional medical clinic for CSHCN. Paid claims were merged for the state-funded clinic, a Medicaid managed-care plan, and a private HMO. Health-care expenditures totaled over $8 million during the study year. Eighteen children accounted for 46% of the expenditures. Multiple payment sources were needed to accurately estimate the cost of care for CSHCN. The greatest costs were associated with catastrophic illness and hospitalization for a few very ill children.