BACKGROUND A difficultly retrieved, impacted distal common bile duct stone is sometimes encountered during supraduodenal common bile duct exploration. Transduodenal sphincteroplasty is usually performed when such stones cannot be retrieved by conventional methods, but not without risk. OBJECTIVE To achieve clearance of such complicated stones and to avoid the potential risks of transduodenal sphincteroplasty. METHODS Prospective clinical trial. METHODS Medical college-affiliated hospital and tertiary care center. METHODS From July 1991 to April 1993, 10 patients met the following inclusion criteria: (1) an impacted distal common bile duct stone found during supraduodenal common bile duct exploration and (2) failure of conventional methods such as stone forceps, a basket, flushing with normal saline solution, or a Fogarty catheter to retrieve stones via the supraduodenal choledochotomy. Another 10 patients with the same problem, treated with transduodenal sphincteroplasty from February 1989 to May 1991, were used as a comparison group. METHODS Intraoperative choledochoscopic electrohydraulic lithotripsy was applied with continuous visualization through a choledochoscope. METHODS Effectiveness of stone fragmentation and possible complications. RESULTS Stones were fragmented and successfully removed by a basket and flushing with normal saline solution. Mild oozing was noted in one patient, but soon stopped spontaneously. The mean operative time of the clinical trial group was significantly shorter (P = .004) than that of the comparison group; the mean postoperative stay was 4 days shorter. The complication rate of the clinical trial group (10%) was lower than that of the comparison group (40%). The 10 successfully treated patients of the clinical trial group remain well, with a mean follow-up of 22 months. CONCLUSIONS Intraoperative choledochoscopic electrohydraulic lithotripsy is a safe and effective method for removal of impacted distal common bile duct stones.