Obstructive jaundice in the adult is usually caused by biliary tract calculi or neoplasms, hepatotoxic drugs, and, less commonly, a cholangiolitic form of infectious hepatitis. An uncommon cause is biliary obstruction from a pancreatic pseudocyst. The importance of considering compression of the common bile duct by a cyst in the head of the pancreas is the problem of differentiating this lesion from carcinoma. This separation, often impossible by clinical and laboratory methods, is frequently difficult at the time of laparotomy. The diagnostic and therapeutic aspects of this cause of jaundice are illustrated by the present report. Report of a Case A 52-year-old white, married, male hospital housekeeper, was admitted to the Peter Bent Brigham Hospital for the first time in July, 1957, because of jaundice of three days' duration. A chronic alcoholic, he had been in good health until eight months before admission. Since that time he had noted intermittent