OBJECTIVE To determine whether laparoscopic sonography (LS) could be a valid alternative to intraoperative cholangiography (IOC) in the detection of bile duct stones and anatomical variations. METHODS Prospective, controlled study comparing LS and IOC using intraoperative findings and/or postoperative endoscopic retrograde cholangiopancreatography as the gold standard. METHODS Department of Surgery at Zürich University Hospital, Switzerland. METHODS One hundred consecutive patients undergoing laparoscopic cholecystectomy between January 1992 and January 1993. Twenty-three patients were operated on for acute cholecystitis, while the remainder experienced symptomatic bile duct stones. Ninety-six patients underwent preoperative sonography and 85 underwent intravenous cholangiography. Laparoscopic sonography was performed in all patients after dissection of the cystic duct. METHODS A 5.5-MHz sector scanner with a 360 degrees angle and an optimal depth of 1 to 4 cm was used. After LS, IOC was performed with a 4F ureteric catheter and a modern fluoroscope. Patients with bile duct stones were sent for endoscopic retrograde cholangiopancreatography postoperatively or the stones were removed laparoscopically. RESULTS Unsuspected common duct stones in three patients and several small calculi in the cystic duct in one patient were detected intraoperatively. Sensitivities and specificities for the detection of bile duct calculi were 100% and 98% by LS and 75% and 99% by IOC, respectively. Anatomical variations of the extrahepatic bile ducts were detected by LS in 20 patients and by IOC in 21 patients. Laparoscopic sonography visualized variations of the hepatic arteries in 22 patients. The average time consumption for LS was 5.4 minutes (range, 2 to 12 minutes) and 16.4 minutes for IOC (range, 4 to 37 minutes). CONCLUSIONS Laparoscopic sonography is a quick and reliable intraoperative diagnostic tool and could replace IOC in laparoscopic cholecystectomy. Additional trials in a larger patient population are needed for a final assessment.