We determined medical costs and family out-of-pocket expenses over time for 569 children with malignant neoplasms. All medical charges (inpatient and outpatient), family out-of-pocket expenses, and wages lost were collected and annualized. The mean cost of cancer care and treatment per patient-year was $29,708, with variation by diagnosis, prognosis, and year since diagnosis. The mean annual hospital inpatient cost was $15,455; mean ambulatory care cost, $3,806; and family out-of-pocket disease-related expenses, $9,787. Family out-of-pocket expenses added about 50% to the total cost of disease-related care and consumed 38% of gross annual family income; wages lost accounted for nearly half. About 95% of all medical costs was paid by private, public, or charitable payers. Out-of-pocket medical expenses for which the family was responsible were about $1,000 each year. However, all nonmedical, disease-related expenses were borne by the family.