Abstract—Ultra Performance Liquid Chromatography (UPLC) takes the advantage of technological strides made in particle chemistry performance, system optimization, detector design and data processing and control. Using sub 2 mm particles and mobile phases at higher linear velocities and instrumentation that operates at higher pressures than those used in HPLC, dramatic increases in resolution, sensitivity and speed of analysis can be obtained. This new category of analytical separation science retains the practicality and principles of HPLC while creating a step function improvement in chromatographic performance. This review introduces the theory of UPLC and summarizes some of the most recent work in the field.