Superior mesenteric artery (SMA) syndrome is a symptom complex resulting from compression of third portion of duodenum by the root of the small bowel mesentery at the level of the SMA. This syndrome can occur as an acute illness but more commonly it appears as chronic condition. Identification of this syndrome can be a diagnostic dilemma and it is frequently made by exclusion. In our patient, rapid weight loss, nausea and bile stained vomiting were present. Ultrasound and MR-angiography were performed for measuring the angle and the distance between the SMA and the aorta. We confirmed the diagnosis via the reduced aorto-mesenteric angle and distance and the patient was then treated by laparoscopic surgery. After lysis of the ligament of Treitz, the patient's symptom were improved. This syndrome must be considered as one of the causes of upper gastrointestinal obstruction. (Korean J Gastrointest Endosc 2006;32:215220)