A study was performed to evaluate the atrophic changes of the central nerve system after chemotheraphy in the patients with acute leukemia. the computed tomographic findings and medical records 20 proven acute leukemia patients under 35 years-old who developed various CNS symptoms and signs during and/or after 2 coures of chemotheraphy were reviewed. The results were as follows : 1. Age distribution was 14 to 35 years (mean was 26 years) Male was 15. 2. Presenting clinical symptoms and signs were headache (16/20) nausea and vomiting (11/20) and loss of con-sciousness(5/20) 3. Brain atroply was noted in 16 patients including cortical and subcortical atrophy 15 cases and succortical atrophy 1 case. 4. Two cases of hemorrhage one each of intracranial hematoma and chronic subdural hematoma were found in addition to brain artophy. This showed that chemotherapeutic agents cause brain atrophy in a considerable number of the patients with symptomatic acute leukemia.