From November 1994 to March 1996, 150 patients treated by laparoscopic cholecystectomy were included in a prospective study, to compare intraoperative cholangiography (IOC) and laparoscopic ultrasonography (LU). The biliary tree was successively explored by these two methods in the routine detection of common bile duct stones. The feasibility of LU was 100%. Cholangiography was performed only in 125 cases (83%). The time taken for LU was significantly shorter (11.6 vs. 17.6 minutes, p = 0.0001). In this study, common bile duct stones were found in 14 cases (9%). For their detection, results were comparable to LU and IOC. For LU, sensitivity was 80% and specificity 99%; and for IOC, 78 and 97%, respectively. Both examinations combined had a 100% sensitivity and specificity. Laparoscopic ultrasonography failed to recognize the intrapancreatic part of the common bile duct in 25 cases (17%) and did not show anatomic abnormalities detected by IOC. It did, however, detect other unsuspected intraabdominal abnormalities. Although LU is safe, repeatable, and noninvasive, a considerable learning curve is necessary to optimize its efficacy. Comparison of relative cost must be undertaken.