A 48-year-old Japanese woman with Behçet's disease suffered successive rupture of thoracic aortic and cerebral aneurysms within one year. The patient underwent successful surgical treatment for both aneurysms. Histological examination of the aneurysm walls revealed lymphocyte infiltration into the adventitia with smooth muscle cell hyperplasia in the thickened intima. This is an extremely unusual presentation of Behçet's disease associated with both cerebral and aortic aneurysms.