To investigate the difference in the therapeutic effect and complication of the extracorporeal shock wave lithotripsy (ESWL) between patients with non-calcified and calcified gallstones, a total 64 patients (36 with non-calcified gallstones and 28 with calcified gallstones) were selected to undergo ESWL treatment of their gallbladder stones using a piezoelectric lithotripter. Only patients who gave a history of biliary pain and who had fewer than three stones with a maximal diameter of 30 mm were admitted to this study. Treatment with ursodeoxycholic acid at a dose of 10 mg/kg/day was started 1 week before the lithotripsy. The percentage of patients whose gallstones were fragmented to particles under 3 mm was 67%: in the non-calcified gallstone group and 50%. in the calcified gallstone group. There was no significant difference in the fragmentation rate between the two groups (p>0.05). Forty-six percent of patients with non-calcified gallstones were free of stones after 6 months of oral bile acid therapy compared with 14% of those with calcified gallstones (p<0.05). Shock wave therapy had no adverse effects except cutaneous petechia (1.6%), transient gross hematuria (1.6%) and some episodes of abdominal pain (30%). Acute cholecystitis occured in 5% of the patients. One patient underwent elective