The results of clinical application of an extracorporeal shock wave lithotripter (MFL-5000, Dornier, Germany) were presented. The treatments were performed from August 1989 to November 1989 at the University of Tokyo. A total of 40 sessions were carried out on 32 patients with 51 upper urinary tract stones. On the X-ray films obtained three months after the last sessions, 10 patients (34.5%) were free from stone fragments and 4 (13.8%) had stone fragments equal or less than 4 mm. After treatment no serious adverse effect was observed. Macroscopic hematuria was observed in almost all patients, pyrexia in 7 (21.9%), and flank pain in 6 (18.8%). On the laboratory data after treatments, there were slight and transient changes which were milder than those of the first generation lithotripter. It is concluded that MFL-5000 is useful and safe in the management of patients with upper urinary tract stones.