Pancreatic pseudocysts are a well-recognized complication of pancreatitis. Most occur in or adjacent to the pancreas. Occasionally, duodenal involvement may occur due to the nonperitonealized posterior surface of the duodenum is in direct contact with the head of the pancreas. But there is little awareness of the intramural and major extrinsic involvement of the duodenum with also occurs. A case was recently experienced involving an intramural pancreatic pseudocyst of the duodenum. (Korean J Gastrointest Endosc 2000;20:58 62)