This study presents retrospective analyses of 20 acute lymphoblastic leukemia (ALL) patients who developed neurologic complications (except leukemic infiltration). These subjects represent 9.9% of 203 ALL patients aged 16 years or younger followed in our hospital between March 1991 and January 2003. Fourteen male and six female patients, whose ages ranged between 6 and 168 months, developed 24 episodes of neurologic complications after the diagnosis of ALL. The most common complication was meningitis, which developed in six (25%) episodes, and two thirds of the patients who had meningitis were evaluated to be iatrogenic. Cerebral infarct and venous thrombosis were detected in five (21%) of the episodes. In two (8%) episodes progressive cerebral dysfunction developed after radiotherapy. The remaining 11 (45%) episodes are due to varying types of complications. Interestingly, one patient had abundant histiocytes exhibiting hemophagocytosis in the cerebrospinal fluid (CSF) examination and this patient was subsequently diagnosed with fungal meningoencephalitis, by further investigation. Six (30%) patients died; epilepsia developed in five (25%) patients in the follow-up period and the remaining nine (45%) are healthy. By close follow-up and effective treatment of thrombosis and, especially, of infections including iatrogenic meningitis in developing countries, the morbidities and mortalities of these complications can be decreased. (C) 2005 Elsevier Ltd. All rights reserved.