In this report, we present a twenty-nine year old patient with a five-year history of Behcet's disease (BD), who developed an ascending aortic aneurysm. Chest enhanced computed tomography scanning demonstrated a saccular aneurysm of the ascending aorta, with a maximum diameter of 11 cm. The patient was administered with prednisone、thalidomide and anticoagulant. A regular follow up was carried out. The patient lived well with blood sedimentation and C-reactive protein in the normal range.Keywords: Behcet's disease, ascending aortic aneurysm, thalidomide, anticoagulation prosthetic graft was utilized. No pathological examination was performed. Cervical vascular murmur disappeared after the surgery. Three years later,before admission to our department, he was worried about recurrent oral and genital ulcers. Physical examination showed multiple ulcers on mouth mucosa and skin of scrotum and swelling in the superior extremity of the chest; the diameter of the basilar part was about 5 cm, and the cutaneous pathergy test was positive. Blood examination showed a white blood cell count, red blood cell count, and hemoglobin, all in the normal range; blood sedimentation was 35 mm per hour, and C-reactive protein was 208 mg per liter. The blood culture was negative. Chest enhanced computed tomography scanning demonstrated that the patient has a saccular aneurysm on the ascending aorta with a diameter of 6 × 9 × 11 cm. The aneurysm showed a big cavity, combined with thrombosis (Figs. 2 and 3).The diagnosis relied upon the criteria proposed by the International Study Group for Behcet's disease. Because of poor economical conditions, the patient refused a second operation and accepted medicinal therapy. Medicinal therapy included oral prednisone 30 mg once per day, thalidomide 100 mg once per night, aspirin 100 mg once per day, aceclofenac 50 mg twice per day. Prednisone was decrement gradually to 10 mg per day as the mucosa ulcer improved. A regular follow-up was carried out strictly for eighteen months. The patient is asymptomatic and lives well now. He comes to our outpatient room, once a month.