In Japan Wernicke's encephalopathy is not rare, but only one case of Marchiafava-Bignami disease has been reported. In our case, Wernicke lesions were found in the mamillary bodies, septal nuclei, and periventricular regions. Involvement of the septal nuclei is rare in this encephalopathy. A characteristic Marchiafava-Bignami lesion was observed only in the anterior part of the corpus callosum. From the clinicopathologic viewpoint, Wernicke's encephalopathy might have preceded Marchiafava-Bignami disease in our case. To our knowledge, only two cases without a history of alcoholism and both suffering from Wernicke's encephalopathy and Marchiafava-Bignami disease have been documented. However, in both cases Wernicke lesions were atypical, since characteristic lesions were absent in the mamillary bodies and in the regions surrounding the third ventricle and the aqueduct. Ours appears to be the first report on a non-alcoholic patient with typical lesions of both diseases.