To compare the irrigation flows between different irrigation methods for f-URS.We compared the automatic irrigation system Endoflow II to gravity-based irrigation, and gravity-based irrigation with pressure cuff. Irrigation pressures were set at 40 and 100cmHIrrigations flows remained constant over the time for the Endoflow II and the gravity-based irrigation methods regardless of the irrigation pressure and setting. For the pressure cuff method, the irrigation flow remained constant only when the working channel was occupied either by the nitinol basket or the laser fiber. Irrigation flow with the Endoflow II were constantly higher than gravity-based irrigation methods. Irrigation flow significantly increased with increased irrigation pressure. In the presence of any instruments at any irrigation pressure, the flow decreased as the size of the instrument in the working channel increased.Automatic irrigation system Endoflow II provided higher irrigation flows than gravity-based irrigation methods. The irrigation flow decreased as the size of the instrument in the working channel increased. Further studies conducted in vivo are needed to investigate if the differences found between irrigation methods result in higher intrarenal pressure during procedures.4.