Bile duct stones that can't be removed by conventional means can often be removed after fragmentation by shock waves (lithotripsy). The shock waves that are used for fragmentation of these stones are generated by electric sparks (electrohydraulic lithotripsy) or laser (laser lithotripsy). Although both techniques have been used for many years, there are no studies comparing the efficacy of the two. The purpose of this study is to find out which technique is more effective.