WE ARE reporting from the Surgical Service of the University of Colorado School of Medicine 100 consecutive cases of exploration of the common bile duct in an effort to determine the positive incidence of choledocholithiasis, and the relation between jaundice and choledocholithiasis; and to determine whether choledocholithiasis develops as a new condition following previous cholecystectomy. In 290 cholecystectomies, choledochotomy was performed 100 times, or 34%. In no instance in this series—as proved by the necessity for reexploration—was there failure to explore a duct which was obstructed by calculus. In three instances,reexploration of the duct was required to correct obstruction which had not been relieved at the initial operation. Our error, then, has not been attributable to our criteria for exploring the common duct, but rather to our failure to make sure of removing all obstructing calculi which were present (Table 1). If there is doubt that a patent duct