Purpose. This study was conducted to compare the fluid warming capabilities at different flow rates in four different warming systems. Methods. The intravenous (IV) fluid warmers used in this study were a water-bath warmer, a forced-air warmer, a dry-heat plate warmer, and an IV fluid tube warmer. Ringer's solution at room temperature or at ice-cold temperature (120–3000 ml·h−1) was used as an IV fluid, and the IV fluid temperatures were measured with thermocouples at the end of a 1-m tube connected to the warmer. Results. The temperature of the IV fluid delivered by the water bath and the forced-air warming system increased as the flow rate increased up to 1200 ml·h−1 but decreased with further increase of the flow rate. The temperature of the IV fluid delivered by the dry-heat plate warmer significantly increased as the flow rate increased within the range studied. The delivered temperature did not depend on the flow rate within the range studied when the IV fluid tube warmer was used. Conclusion. It is important to choose a warmer according to its characteristics as well as its performance.