Our experience supports the concept that acute and chronic pancreatic pseudocysts differ and require different plans of management. Patients who present with a chronic pseudocyst should be scheduled for operation promptly; internal drainage is almost always possible, spontaneous resolution is extremely rare, and delay only runs the risk of complications. Patients who are found to have an acute pseudocyst that develops during an attack of acute pancreatitis should be managed expectantly for 4 to 6 weeks; in them, spontaneous resolution may occur and surgical therapy is more satisfactory if the pseudocyst wall is allowed to mature enough that internal drainage is possible.