A case report of spontaneous dissection of the superior mesenteric artery (SMA) in a 53-year-old man who complained of sudden colic-midabdominal pain is presented. In this case, ultrasonography is very usefull for early diagnosis of dissection, and this is successfully treated by Ao-AMS bypass with excision of the proximal segment of SMA. Postoperatively the patient has no symptoms for 2 years.