[en] Brain MRI findings of treatment-related white matter abnormality in childhood leukemia or lymphoma were reviewed. MRI study was performed in 64 patients and they were divided into three groups according to their clinical courses. Group 1 (G-1) consisted of 22 patients during chemotherapy including 7 relapsed cases. Group 2 (G-2) included 16 patients within 1 year after chemotherapy off and Group 3 (G-3) included 22 patients elapsed more than 1 year after chemotherapy off. High intensity area in white matter on proton- and T2-weighted images was judged abnormal. There were 14 (22%) abnormal cases in total and each group had 7 (32%), 2 (13%), and 5 (19%) cases, respectively. All abnormal subjects except four in G-1 had received whole cranial irradiation. High dose methotrexate therapy had been given in all abnormal cases of G-1 and G-2 and 2 cases of G-3. High intensity area seemed to extend more widely in G-1 than the others. In G-1, high intensity tended to appear in early phase of the therapy and some regression was observed in initially treated cases during short-term follow up. The relations between these MRI findings and the histopathologic findings previously reported are discussed. (author)