The results of extracorporeal shock wave lithotrity (Dornier lithotriptor) for 700 cases of urinary calculi have been reviewed and correlated with the radiological features of the calculi in order to define some predictive radiological criteria of effectiveness. The calculi were broken up in 74.5% of all cases, complete destruction (no residual fragment) was achieved in 34.5% and partial destruction in 40% of cases. The rate of failure (failure to break up or scatter the calculus) is 8.9%. Complications were observed in 2.6% of all cases, a second session of lithotrity or a surgical operation was required in 4.8% of cases (evolution lost to follow-up: 9.2%). The comparison of these results with the radiological data obtained before lithotrity allows distinguishing 2 categories of calculi: 1) Calculi with a favorable prognosis: single, smaller than 1 cm, pyelic, not very opaque and heterogeneous, located in normal-sized cavities; 2) calculi with a poor prognosis: multiple, larger than 2 cm, lower calyceal or ureteral, very opaque and homogeneous, located within dilated cavities.