OBJECTIVES: Impacted ureteral stones remain a great challenge to urologists in performing ureteroscopic lithotripsy. We report our experiences in ureteroscopic management of ureteral stones larger than 15mm. PATIENTS AND METHODS: From January 2003 to June 2006, 31 admitted patients (18 men, 13 women, mean age: 50.8 years old) with impacted ureteral stones were analyzed retrospectively. Among them, 22 stones were located in upper ureter while 9 in middle portion. The greatest dimension of the stone was at least 15mm (ranged 15-35 mm, mean diameter: 18.2mm) with mean stone burden 230 mm2 (ranged: 150 mm^2-850 mm^2). Six Fr. rigid ureteroscope was used in 20 patients and 8F rigid scope in 11 patients. All the stones were treated with pneumatic lithoclast and were crushed into fragments smaller than 3 mm to facilitate passage. Post-operative KUB was taken after one week and one month for evaluating stone-free rate. RESULTS: The mean operative time was 55 minutes (ranged 39 to 84 minutes). Post-operatively, stones were crushed totally and passed out in 24 patients. Three patients had residual ureteral stones in situ in which 2 of them were managed by secondary ureteroscopy and the other by percutaneous access removal. 4 pushed-back stones were further treated by SWL. Ureteral perforation was noted in 3 patients and was managed by either retrograde or antegrade ureteral stenting satisfactorily without sequelae of ureteral strictures during followup at 9 months. CONCLUSIONS: Stone-free rate was 77.4% after one session ureteroscopy. Residual stone or pushed back stone could be successfully treated by secondary ureteroscopy, SWL or percutaneous access removal. Ureteroscopic lithotripsy for impacted ureteral stones can be done effectively by pneumatic lithotripter with mild complication.