Central nervous system (CNS) involvement in Behçet's disease, usually called neuro-Behçet's syndrome (NB), is one of the most serious complications of the disease. In the present study, we carried out immunohistological examination of biopsied or autopsied brain tissues from 3 patients with different types of NB, acute NB, chronic progressive NB, and NB in a long-term remission. Histopathology of mass lesion in acute NB revealed infiltration of mononuclear cells around small vessels, consisting of CD45RO+ T lymphocytes and CD68+ monocytes with few CD20+ B lymphocytes. Of interest, TUNNEL staining disclosed that most neurons were undergoing apoptosis in the inflammatory lesion. In chronic progressive NB, similar histopathological changes were noted in pons, cerebellum, medulla, internal capsule, and midbrain, although the degree of mononuclear cell infiltration was modest. There were also scattered foci of neurons undergoing apoptosis with formation of a few binucleated neurons. The most prominent feature of NB in a long-term remission was atrophy of basal pons with formation of cystic or moth-eaten lesions, consisting of isomorphic gliosis with viable neurons. There were still scattered foci of perivascular cuffing of T lymphocytes and monocytes. These results emphasize the common features throughout the courses of NB, perivascular cuffing of T lymphocytes and monocytes, irrespective of the clinical phenotypes. More importantly, it is suggested that soluble factors produced by infiltrating cells, including IL-6, might play a role in the induction of apoptosis of neurons in NB.