A policy of limiting preoperative diagnostic imaging of pancreatic pseudocysts to barium studies, sonography, or computed tomography will result in failure to detect frequently associated lesions which may only be appreciated by arteriography and which radically alter both the prognosis and surgical approach. These associated lesions include: (1) pseudoaneurysms, probably the most common cause of major gastrointestinal hemorrhage in pseudocyst patients; (2) pancreatic carcinoma, a possible etiologic factor leading to formation of the pseudocyst; (3) benign or malignant cystadenomas which mimic pseudocysts clinically but can be usually identified arteriographically by prominant neovascularity; and (4) splenic vein obstruction which can produce extrahepatic portal hypertension and necessitate splenectomy. In our experience, these complicating lesions are relatively common. Their preoperative detection is desirable and is best accomplished by arteriography. For this reason, arteriography should be routinely performed in patients suspected of pancreatic pseudocyst.