A total of 1,241 calculi corresponding to 1,000 patients were treated with the piezoelectric EDAP-LTO1 lithotriptor. All but 1% of the calculi could be localized by ultrasonic imaging. Stone localization was easily achieved in 80% and with some difficulty in 19% of the cases. All patients had a minimum follow-up of 3 months. Stone fragmentation was accomplished in 91% of pyelic, 86% of upper, 55% of mid, 90% of lower caliceal, and 37% of staghorn calculi. Fragmentation was achieved in 4 of 5 calculi in the lumbar ureter and 5 of 11 calculi in the pelvic ureter that were treated in situ. The material and method for extracorporeal shock wave lithotripsy using ultrasonic imaging are described. The advantages and disadvantages of ultrasound versus radiologic stone localization are discussed.