Annular pancreas is a rare congenital anomaly, which consists of a ring of pancreatic tissue partially or completely encircling the descending portion of the duodenum. We reported a case of symptomatic annular pancreas in a 40 year-old man admitted to our hospital complaining of abdominal pain, nausea and vomiting without body weight loss in January 2000. The patient underwent laparoscopic cholecystectomy for acalculous cholecystitis in September 1996. Initially, he was diagnosed with duodenal stenosis due to a duodenal ulcer scar, but laboratory data showed no abnormalities. His symptoms did not improve with medication or endoscopic balloon dilatation. Duodenograpy revealed a narrow segment with a smooth mucosal surface in the 2nd portion of the duodenal loop in the duodenum, and a computed tomography (CT) scan demonstrated a thickened pancreas head around this narrow segment. We were therefore able to diagnose annular pancreas. A duodeno-duodenostomy was performed in March 2000. The patient's postoperative course was uneventful, and he was discharged from our hospital on the 19th postoperative day. Although define diagnosis of annular pancreas is frequently made at laparotomy, the development of a recurrent imaging modality might assist in the preoperative diagnosis.