The feeling of frustration experienced upon noting an overlooked stone on a postoperative cholangiogram following what was thought to be a perfectly complete and satisfactory exploration of the common duct has prompted us to evaluate operative cholangiography. Our approach to the problem is indicated by the question "What will operative cholangiography add to what we now accomplish in surgery of the biliary tract, and what disadvantages will be encountered?" Nomenclature Operative cholangiography is the roentgenologic examination of the biliary tract with the aid of radiopaque medium instilled into the bile ducts, usually through a tube or needle, during the actual operation. Much has been written about the procedure,* and we shall not go into the history. We shall point out that the term "cholangiogram" refers to a depiction not only of the common bile duct but of all the radicles of the biliary tree as well. In a discussion of