Hemorrhage is an uncommon but serious cornplicaticm of pancreatic pseudocysts. When gastrointestinal bleeding or intra-abdominal hemorrhage is associated with a pancreatic pseudocyst and the usual sources of bleeding are not detected by endoscopy, the rupture of a pseudoaneurysm inside the pseudocyst should be suspeeted. We report four cases presenting with major bleeding. Bleeding was massive in two patients and intermittent in two. It resulted from erosion of the gastroduodenal artery in two patients, bleeding into the pancreatic duct in one patient, erosion of the duodenum by a bleeding pseudocyst in one and involvement of the spleen by a bleeding pseudocyst in one. Of the four patients with bleeding pseudocysts, two underwent primary pancreatic reseetion and the other two underwent transcatheter embolization with embolus coiL Bleeding was successfully controlled by the transcatheter arterial embolization in one out of the two patient and pancreatic resection was performed in the rest of three patients. (Korean J Gastroenterol 1997; 29:266-273)