The trend toward high-speed LC analysis with reduced column particle sizes continues to increase in popularity. The narrow peak widths of high-speed LC have generally been handled adequately with UV detectors by increasing data acquisition rates. However, use of a MS will reduce the risk of misidentifying peaks when transferring methods from conventional to high-speed LC. Most MS instruments have had difficulty keeping up with these sharp peaks, which may have peak widths of 200 milliseconds or less. Accurate mass analysis of sharp chromatographic peaks obtained by high-speed LC requires ultra-fast MS detection capabilities. A number of high-speed separations will be evaluated using MS scanning speeds of up to 15,000 u/sec with polarity switching speeds of 15 msec.