Although the evidence is sparse, most urologists advise the insertion of a safety guide wire (SGW) alongside the ureteroscope whenever performing ureteroscopy (URS). The aim of the study was to compare the results of ureteroscopic treatment for ureteral stones at the Oslo University Hospital (OUH), where the SGW is routinely used, with the results at the Haukeland University Hospital (HUH), where the SGW is routinely omitted. The primary goal was to evaluate the success rates of passing the ureteroscope through the orifice, the ability to access the ureteral stone, and the ability to place a ureteral stent when needed after the endoscopy. The secondary goals were to compare the perioperative complication rates and stone-free rates at the two hospitals.