Objectives: To study the outcome and safety of semirigid ureteroscopy (URS) using pneumatic lithotripsy for treatment of ureteral stones of surface area > 2 and to assess the impact of size and location on stone-free (SF) rate. Patients and Methods: In this study, 265 patients with > mm 2 isolated ureteral stones treated by semirigid URS were included. URS was performed using an 8F, 7F, or 6.4F semirigid ureteroscopes with pneumatic lithotripsy (Swiss Lithoclast). Stones were fragmented to ~23mm particles, and removed. The outcome parameters assessed at 3-month follow-up were SF rate and efficiency quotient (EQ); impact of stone size and site on SF/EQ was also analyzed. The patient demographics, stone, procedure, and patient-related parameters and complications were noted. Results: At 3-month follow-up overall SF was 74% and EQ 59.2%. SF for 30100mm2 and >100mm2 was 79.2% and 68.5%, respectively p<0.003). The SF/EQ for upper, middle, and lower ureteral stones were 59/40.7, 53/37.5, and 92/84.5, respectively p<0.001). There was no major complication; the minor complication rate was 12.5%. Conclusions: Semirigid URS using pneumatic lithotripsy for treatment of stones >30mm2 is a safe and highly efficacious procedure particularly in the distal ureter. There is a significant difference in the SF and EQ between upper/middle ureteral stone and lower ureteral stone. Stone size has a direct relation with the SF and EQ. Upper ureteral stones have a longer time to SF compared to middle and lower ureteral stones p<0.001).