We have described a spectrum of pancreatic surgery after cardiopulmonary bypass. At one end is a subclinical lesion which was manifested only by elevations in serum isoamylase levels (27 percent of patients) and increased ribonuclease levels (13 percent of patients) in asymptomatic patients followed after cardiac surgery. At the other end is a severe and often lethal necrotizing pancreatitis. Acute necrotizing pancreatitis was found at autopsy in 25 percent of 138 patients who died after cardiac surgery, and it correlated strongly with low output, acute tubular necrosis, and infarction of the liver, spleen, or bowel. It was the principal cause of death in 4 percent of these patients. In addition, 24 percent of 38 nonsurgical patients who died from cardiac failure and hypoperfusion had acute pancreatitis at autopsy, whereas acute pancreatitis was not observed in 55 nonsurgical patients who died without a significant period of low output. Acute pancreatitis was recognized postoperatively in 12 patients (0.2 percent). Three had mild pancreatitis, and all responded well to conservative therapy. In nine patients, fulminant necrotizing pancreatitis developed. Their courses were characterized by significant early postoperative hemodynamic compromise, abdominal distention, ileus, fever, and episodes of late vascular instability associated with hypocalcemia. The diagnosis of pancreatitis was usually missed because of the absence of pain, tenderness and hyperamylasemia. The diagnosis was confirmed at laparotomy in eight patients and at autopsy in one. The only two survivors among the nine with severe cases had aggressive mobilization, debridement, and wide drainage of the necrotic pancreas. We suggest that a mild subclinical injury to the pancreas may occur as a consequence of cardiopulmonary bypass and may progress to severe ischemic necrosis if hypoperfusion follows in the postoperative period, the presentation of necrotizing pancreatitis may be atypical in the cardiac surgical patient and should be considered if nonspecific abdominal symptoms are present, and aggressive debridement and drainage may be the optimal treatment for aggressive forms of this disease.