The aim of this prospective study was the comparison of laparoscopic sonography with intraoperative cholangiography (IOC) during laparoscopic cholecystectomy. A 360 degree-sector scanner with a frequency of 5.5 MHz was used. The examination was successful in all 69 patients entered into the study. In the beginning 19 patients were examined sonographically without subsequent IOC. None of these patients had bile duct stones and their postoperative history was uneventful. In the 50 patients operated on subsequently both laparoscopic sonography and IOC were tried. IOC was not performed due to technical failure in 4 patients and due to allergic reactions to contrast media in one patient. Thirty-one patients demonstrated normal bile ducts without stones in both examinations. Ten patients had dilated ducts without stones. In three cases a stone was seen on IOC and intraoperative sonography. In one case a duodenal diverticulum containing debris, demonstrated by IOC, was the reason for a false positive sonographic finding. Sensitivity and specificity of laparoscopic sonography concerning the visualisation of bile duct stones were 100 and 98%, respectively. The time necessary for the examination was significantly shorter in laparoscopic sonography than in intraoperative cholangiography (p = 0.0001). If these results can be reproduced in a larger population of patients, laparoscopic sonography can be considered a safe, fast and non-invasive alternative to intraoperative cholangiography.