In the present paper an autopsy case report of Neuro-Behçet's syndrome has been made and patho-histological studies of the brain of the 8 autopsy cases reported previously as well as those of the present case have been conducted. The present case was a 47-years old man. In the ninth years after the onset of symptoms in the oral cavity and in the genitalia he was troubled repeatedly with diplopia. Gradually there appeared such symptoms as the disturbance of his gait, forced laughing, disturbance of speech, ataxia, and the inflammation at the sites of injection. He had remission and aggravation of these symptoms. However, he died of respiratory paralysis 17 years after the onset of oral aphtha and 8 years after the onset of diplopia. In the patho-histological observation of this case there were seen perivascular cell infiltration covering the entire cerebral parenchyma as well as a portion of meninges, revealing a picture of chronic disseminated panmeningoencephalitis and cerebral abscess of medulla oblongata. In addition, there were fibrinoid degeneration of the blood vessel wall and such degenerative changes in the blood vessels as fibrosis and proliferation of collagen fibers; and also circumscribed foci of glia cell proliferation, softening cavities and abnomal proliferation of consumptive pigments. These pathlogical changes were recognized in the entire brain, but they were especially prominent in brain-stem. There were no pathologica changes in the optic nerves and in the spinal cord. In the investigations of the patho-histological picture of the brain in our case as well as in the cases reported in literature, the common findings in Neuro-Behçet's syndrome are extensive disseminated perivascular cell infiltration of the brain, softning accompanied by a moderate proliferation of microglia cells and degenerative changes of the blood vessel wall. while these pathological changes are especially marked in the brain-stem, to a greater degree in the white matter than in the grey matter. Neuro-Behçet's syndrome has been found to resemble periarteritis nodosa and clinically it shows many common pathologic changes as found in collagene disease. Hence, it is assumed that Behçet's syndrome belongs to the collagene disease.