To determine the sensitivity of sonography in the detection of choledocholithiasis, the sonograms of 138 patients with surgically proven common bile duct stones were reviewed. A definite diagnosis of choledocholithiasis could be made on the basis of the sonograms in 22% of cases. Overall, 23% had common ducts of normal caliber (less than or equal to 7 mm diam) and 23% had normal total bilirubin levels at the time of the examination. Although a sonographic diagnosis of choledocholithiasis provides important information for the surgeon, the method is not sufficiently sensitive to serve as a definitive preoperative test for common bile duct stones.