Clinical studies of acute pancreatitis have been hampered by the fact that the accuracy of the clinical diagnosis is often questionable.2,14,17 Although recent reviews have been more critical of cases selected for analysis,4 a more complete retrospective study of proved examples of acute pancreatitis seemed desirable in order to evaluate more precisely the diagnostic criteria, the development of serious complications, and the influence of various forms of therapy. A review was made of the records of 354 patients admitted to the San Francisco General Hospital between 1942 and 1961 who had a diagnosis of acute pancreatitis. In order for a patient to be included in our study group, at least one of the following strict criteria had to be met: (1) the diagnosis of acute pancreatitis was confirmed or made at operation; (2) the diagnosis of acute pancreatitis was established at autopsy; or (3) the presence of a