Cases of exploratory choledochotomy with widened bile duct as the indication have been assessed with respect to missed bile duct concretion in a retrospective study covering a period of five years. During this period 2,000 cholecystectomies were performed. The 110 cases, in which (a) pre-exploratory cholangiography was completely normal apart from a diameter of more than 10 mm, (b) exploratory choledochotomy was performed, and (c) secondary cholangiography had been carried out, were studied in detail. No calculi were demonstrable either at exploratory surgery or secondary cholangiography. With a good radiographic technique it does not seem likely that bile duct concretions would be missed in widened ducts at otherwise normal operative cholangiography--at any rate not with bile duct diameters up to 20 mm.