Pseudocysts of the pancreas are not an uncommon sequela of acute pancreatitis, chronic pancreatitis, and blunt abdominal trauma with resultant traumatic pancreatitis. Pancreatic pseudocysts should be suspected when the serum amylase remains elevated after apparently satisfactory response to treatment of the acute episode. However, the serum amylase may be normal, and quantitative urinary amylases may establish the diagnosis. Blood calcium levels should be followed during severe episodes. A palpable mass can usually be detected in the upper abdomen, most frequently in the mid-epigastrium or the left upper quadrant. These cysts do not have an epithelial lining as do the true pancreatic cysts. They are most commonly found in the body and tail of the pancreas but also may be found in the neck and head of the pancreas. Ultrasonography, computerized tomographic scans, and retrograde cannulation of the pancreatic duct with injection of dye and x-ray opacification (endoscopic retrograde cholangiopancreatography or ERCP) may demonstrate a pseudocyst. Films of the chest and abdomen may demonstrate elevation of the left hemidiaphragm with or without basilar atelectasis or pleural effusion. Treatment of cysts that do not regress spontaneously consists most commonly of internal drainage via the stomach, duodenum, or jejunum. External tube drainage with subsequent fistula may be rarely indicated. Alternatively, some radiologists may drain mature pseudocysts attached to the posterior wall of the stomach using computerized axial tomography. A transgastric needle and then catheter is introduced via a gastrostomy usually created by the percutaneous endoscopic gastrostomy technique (Plate 10).