We performed extracorporeal shock wave lithotripsy (ESWL) monotherapy on 51 patients with upper urinary tract stones using a Siemens Lithostar (C-tube) from April 1992 to April 1993. On the x-ray film obtained three months after the final ESWL treatments, 24 patients (47%) were free from stone concrements and 22 (43%) had stone fragments less than 4 mm. The over-all success rate was therefore 90.2%. No severe side effects were observed. We also examined the relationship between the degree of fragmentation seen on the immediate post-ESWL x-ray and stone status at 3 months. There was no significant correlation between them and the post-ESWL x-ray did not reflect the stone status at three months. In our experience, ESWL monotherapy using a Siemens Lithostar (C-tube) was a safe and effective treatment for upper urinary tract stones.