Although pancreatitis is not an uncommon precursor of pancreatic pseudocyst, it is usually the chronic or relapsing form of the disease which gives rise to cyst formation. It is rare for an initial attack of acute necrotizing pancreatitis to lead to the development of pseudocyst. In the following case the rapid development of a large pseudocyst in the wake of an initial attack of severe necrotizing pancreatitis produced almost complete gastric obstruction and required early surgical intervention.A 21-year-old man was brought to the hospital by ambulance. Forty-eight hours prior to admission he had had sudden cramping epigastric pain and nausea, which soon subsided. Five hours prior