Endoscopic mechanical lithotripsy (EML) was attempted in 41 patients with common bile duct stones unable to be removed by endoscopic sphincterotomy. These patients had altogether 89 stones with stone size ranged from 5 to 30 mm (mean transverse diameter 16.6 +/- 6.0 mm and mean longitudinal diameter 20.0 +/- 7.1 mm). 31 patients had 34 stones greater than or equal to 20 mm in transverse diameter. The overall stone removal rate was 97.6%. The rate of complete removal of the stone fragments with EML at one time was 78.6% (11/14) for large, 58.8% (10/17) for middle and 0 (0/5) for small incision of the sphincter. In patients with diameter of the distal common bile duct greater than or equal to 14 mm and less than 9 mm the rate was 83.3% and 30.8% respectively and the difference was of significance (P < 0.05). The rate of complete removal for using basket and balloon catheter was 6/10 and 4/9 separately and that for combined used of these two methods 83.3% (10/12). The rate of spontaneous passage of the stone (within one week) was 1/5. It is concluded that complete removal of the stone fragments was related mainly to the length of the incision, diameter of distal common bile duct and methods of removing stone fragments after the crush with lithotripsy basket; when the stone is large and there is the no space around the stone for lithotripsy basket manipulation, a large amount of diluted contrast material is injected into the bile duct so as to increase the space and facilitate the ensonaring of the stone with lithotripsy basket. Hard stones can not be crushed easily, so they constitute one of the reasons of failure.