Objective: To assess the efficacy and safety of extracorporeal shock wave lithotripsy with Modularis Vario Siemens in the management of patients with renal and ureteral stones. Methods: Between 2007 and 2009, 225 outpatients were treated with Siemens Modularis Vario lithotripter at Sultan Qaboos University Hospital. Stone size, location, total number of shockwaves, stone-free rate, complications and adjunctive interventions were investigated. Chi-Square and Logistic Regression analyses were used, with p<0.05 set as the level of significance. Results: Of the 225 initial consecutive patients who underwent extracorporeal shock wave lithotripsy, 192 (85%) had renal stones and 33 (15%) had ureteric stones. The mean±SD stone size was 11.3 ± 4.5 mm, while the mean age of the patients was 39.9 ± 12.8 years with 68.5% males. The mean renal stone size was 11.6 ± 4.7 mm; a mean of 1.3 sessions was required. The mean ureteric stone size was 9.9 ± 3 mm; and a mean of 1.3 sessions was required. Treatment success (defined as complete clearance of ureteric stones, stone-free or clinically insignificant residual fragments of <4 mm for renal stones) was 74% for renal stones and 88% for ureteric stones. Additional extracorporeal shock wave lithotripsy and ureteroscopy were the most adjunctive procedures used for stone clearance. Complications occurred in 74 patients (38.5%) with renal stones and 13 patients (39.4%) with uretetric stones. The most common complication was loin pain (experienced by 16.7% with renal stones and 21% with ureteric stones). Severe renal colic mandating admission occurred in 2% of patients with renal stones and 6% of patients with ureteric stones. In patients with renal stone, steinstrasse occurred in 3.6% and infection post extracorporeal shock wave lithotripsy in 0.5%. Using Multivariate Logistic Regression analysis, factors found to have significant effect on complete stone clearance were serum creatinine (p=0.004) and the number of shockwaves (p=0.021). Conclusion: Siemens Modularis Vario lithotripter is a safe and effective tool for treating renal and ureteric stones.