The prevalence of CNS involvement of Adamantiadis-Behçet's syndrome (A-Bs) vary widely. Long-term follow-up studies of CNS involvement have rarely been reported. Five patients with CNS involvement, who were followed up from 2 to 9 years, are presented. Clinicolaboratory investigations (cerebrospinal fluid examination, electroencephalogram, brain CAT scan and MRI) were carried out. One patient had four and two patients had two attacks of CNS involvement with various clinical manifestations. The other two patients had a rather chronic course with a single slight CNS attack. Raised proteins and IgG were found in the CSF. Abnormal electroencephalographic findings were detected in three patients. Communicating hydrocephalus and various other abnormalities on CT scan and MRI were noted. All patients received corticosteroids and immunosuppressants during the attack period.