A rare case of neuro-Behçet disease with diffuse demyelination and gliosis of the frontal white matter is reported clinico-pathologically. The disease began with genital ulcer and recurrent oral aphthosis when the patient was 42 years of age. There was erythema, moderate fever, CSF (cerebrospinal fluid)-pleocytosis and elevated CSF-globulin. He was diagnosed as having neuro-Behçet disease and treated with prednisolone. He gradually became euphoric, disinhibited, indifferent and demented. His cranial CT showed diffuse low density areas in the bilateral frontal white matter. He became bedridden, akinetic mute and died from respiratory dysfunction 3 1/2 years after onset. The following neuropathological findings were observed: 1) Moderate demyelination and gliosis was present mainly in the frontal and parietal white matter. 2) There were many micro-spongious necrotic foci in the gray and white matters of the cerebrum, basal ganglia, thalamus, midbrain and pons, some of which were accompanied by gliosis. 3) From 1/2 to 1/3 of all micro-necrotic foci in the frontal white matter were old and accompanied by gliosis. The white matter containing numerous micro-necrotic foci had myelin pallor and gliosis. 4) There was neither micro-necrosis nor gliosis in the occipital lobe. The pathogenetic correlation of white matter lesions with primary and secondary circulatory disturbances is discussed.