Intracranial hemorrhage (ICH) is a rare but devastating complication of childhood immune thrombocytopenia purpura (ITP). A survey of ICH from 1987 to 2000 identified cases of ICH in childhood ITP in the United States. Forty patients with ICH and 80 matched ITP control subjects were accrued. The estimated incidence of ICH was 0.19% to 0.78%. Platelet counts were less than 20 x 10(9)/L in 90% and less than 10 x 10(9)/L in 75% of children with ICH. Eighteen (45%) children developed ICH within 7 days of diagnosis of ITP; for 10 of these, ICH was the presenting feature of ITP. Twelve (30%) children had chronic ITP. Head trauma and hematuria were the most prominent features associated with ICH, identified in 33% and 22.5% of the patients with ICH and 1 and none of the controls (both P < .001). Bleeding beyond petechiae and ecchymoses was also linked to ICH. Mortality was 25%; a further 25% had neurologic sequelae. Strategies by which high-risk children could be identified were considered, and the costs of preventive combination treatment were estimated. Children with severe thrombocytopenia plus head trauma and/or hematuria appeared to be at particularly high risk of ICH. Aggressive treatment of these children may be appropriate.