We sent questionnaires to hospitals in Japan in order to study the incidence and conditions of intracranial hemorrhage (ICH) in children with immune thrombocytopenic purpura (ITP). From 1980 to 1995, 11 cases of ICH were reported in eight patients with ITP at 35 institutions. One patient had ICH four times, but only one patient died of the condition. From 1990 through 1995, ICH occurred in four (0.52%) of 772 patients with ITP. None of the patients died. The platelet count when ICH occurred was 5.2 +/- 3.7 x 10(9)/l (mean +/- SD) (n = 11). Four of the eight patients (1980-1995) had received active treatment [e.g. intravenous immunoglobulin G (i.v. IgG)] immediately before ICH occurred. In seven cases (1980-1995), possible causes of ICH, including menstruation (n = 2) and viral infections (n = 3), were identified. Systemic lupus erythematosus (SLE) later developed in three patients. Although the incidence of ICH in children with ITP has not decreased compared with the rates in earlier studies, the mortality rate has decreased markedly. Our results suggest that menstruation, infection, and risk factors for progression to SLE may help to predict ICH in children with ITP. Large-scale prospective trials are needed to identify risk factors for ICH.