A novel liquid chromatographic system which enables high temperature ultrafast liquid chromatography (HTUFLC) has been designed through the careful consideration of heat transfer, band broadening, and pressure drop. Studies of the effect of linear velocity on the HETP show that column efficiency at high velocity, especially of well-retained solutes, dramatically improves at higher temperatures. At 150 °C, at a flow rate of 15 mL/min with a 5 cm by 4.6 mm (i.d.) column packed with 3 μm polystyrenecoated zirconia porous particles, long chain alkylphenones were completely resolved, and the analysis time could be decreased by a factor of 50 compared to that at room temperature (25 °C) at a conventional flow rate (4 mL/min). In addition, using pure water as the mobile phase, five phenols were separated in less than 30 s.