Patients and Methods: The ureteroscopic stone removal procedures using the Lithoclast® lithotripsy performed at the Department of Urology B and C without evidence of preoperative urinary tract infection clinically and on laboratory were randomized into 2 groups: Group 1: Amoxicillin + acid clavulanic (Curam® 1.2g), single shot 30 minutes preroperatively; Group 2: Amoxicillin + acid clavulanic administerd right from end of procedure till discharge or urethral catheter removal.