Between May 1994 and March 1996, a total of 427 cases of upper urinary tract stones were treated by extracorporeal shock wave lithotripsy (ESWL) using a Siemens Lithostar2. Of 427 patients, 167 had renal stones and 260 had ureteral calculi. A double J stent was inserted preoperatively for patients with stones > or = 20 mm in diameter. The success rate after 3 months, defined as complete disappearance of stone or partial disintegration with residual stones < or = 4 mm in diameter, was 82.4% and 88.1% for the renal and ureteral calculi, respectively. Additional treatments were required in 9 cases (transurethral ureterolithotripsy in 5, percutaneous nephrostomy in 2, nephrolithotripsy and ureterolithotomy in 1 each). There were no serious side effects requiring surgical treatment or blood transfusion, although perirenal hematoma developed in 5 patients, who were treated conservatively. It is concluded that ESWL using Simens Lithostar 2 is safe and useful for treating upper urinary tract stones.