From September 1988 to April 1989, 400 patients with stones in the calix (40%), in the renal pelvis (45%), in the ureter (15%) and with staghorn calculi (5%), underwent shock wave treatment. In the majority of patients therapy was carried out with general anesthesia. Disintegration was achieved in 95% of stones in the kidney and 44% of stones localized in the ureter following in situ ESWL. The ureteronephroscopy and stone push-up with replacement into the renal pelvis was performed in 56% of ureteral calculi. The average number of impulses to achieve disintegration was 1,850. In 20 patients 4,000 shock waves were necessary. We studied these patients with echotomography, CT scan and magnetic resonance imaging 48 hours after the treatment. The aim of this trial was to assess the efficacy and cost benefit ratio of the Tripter X1 lithotripter.