Annular pancreas is a rare congenital anomaly characterized by the presence of ectopic pancreatic tissue surrounding the descending part of the duodenum. It is one of the few congenital anomalies of the gastrointestinal tract which can produce symptoms late in life. In adults, the factors initiating symptoms are recurrent pancreatitis, duodenal stenosis at the site of the annulus, or duodenal or gastric ulceration. We report a new case involving a 24-year-old woman hospitalised for epigastric pain, nausea and vomiting. Radiological examination was consisted with an annular pancreas. At operation a complete obstruction of the second part of the duodenum was found, caused by an annular pancreas, no other congenital anomaly of the intra-abdominal organs was noted. A gastroenterostomy was performed.