We conducted a comparative analysis of the autopsy findings in a case of Marchiafava-Bignami disease with the X-ray computed tomography (CT) and magnetic resonance imaging (MRI) findings obtained while the patient was alive. Histologically, massive deposits of hemosiderin were demonstrated in the astrocytes and macrophages located in the walls of the callosal cystic lesion, suggesting that the transient increase in density during the subacute stage observed on X-ray CT is secondary to significant hemorrhage.