To ascertain the best diagnostic indicators of choledocholithiasis and to decrease the incidence of retained stones in the common bile duct after exploration, the authors carried out a retrospective review of 110 consecutive patients who underwent common bile duct exploration for calculous biliary tract disease. Conditions that were most often associated with choledocholithiasis were cholangitis and clinically obvious jaundice. The serum bilirubin level was helpful in identifying patients with stones in the common bile duct only when the value was greater than 6 mg/dl (103 mumol/l), and alkaline phosphatase only when the value was more than 250 IU (normal 110 IU). When stones are felt in the duct at operation, the diagnosis of choledocholithiasis is certain; positive operative cholangiograms are highly reliable and the coexistence of small gallstones and a dilated cystic duct is suggestive. The retention of stones is best prevented by careful exploration followed by high-quality T-tube cholangiography performed at operation after the exploration is complete. Any missed stones found in this way should be removed by re-exploration at the time of the original operation. Stones left in the common bile duct are best extracted nonoperatively under radiologic control. This technique, while effective and safe, is associated with considerable morbidity.