With the discovery of vitamin K and the development of methods for measuring plasma prothrombin levels, operation on the jaundiced patient lost much of its terror. By simple preoperative and postoperative procedures, abnormal bleeding in most cases of obstruction of the common duct, whether by stone, tumor or stricture, can now be anticipated and prevented. The liver in these cases is usually normal or so little impaired that the prothrombin level is rapidly brought to normal when the body is given an adequate amount of vitamin K and of bile or bile salts. It has been well established that if the prothrombin level remains normal, unusual bleeding in uncomplicated obstruction of the common duct does not occur. The diagnosis of common duct stone may often be fairly clear, particularly when gallbladder colic, chills, fever and jaundice are present. The preoperative diagnosis of carcinoma of the head of the pancreas or