CT scan in 4 patients with Marchiafava-Bignami's disease in its acute alcoholic form, who died after 12, 18, 30 and 50 days respectively, demonstrated large symmetrical bilateral hypodense areas in the hemispheric white substance. These areas were either widespread or more marked posteriorly, and were independent of the corpus callosum. Pathologic examination of the brains showed necrotic regions, often with cavities, or areas of demyelinization of the centrum ovale correlating with the hypodense areas as seen on CT scans. In two cases CT scan further showed regions of linear hypodensity in front of and medial to the frontal ventricular horns which could have corresponded to the corpus callosum necrosis found on the brain sections. CT scan can thus contribute to the diagnosis of Marchiafava-Bignami's disease.