1-Phenyl-3-methyl-5-pyrazolone (PMP) derivatives of monosaccharides were analyzed by electrophoresis on a quartz microchip with whole-channel UV detection. Rapid separation of PMP derivatives of aldopentoses was achieved by plain-zone electrophoresis in a neutral phosphate buff er with the height equivalent to a theoretical plate at the micrometer level. Zone electrophoresis as borate complexes was also successful for the separation of PMP derivatives of a few aldoses, which were separated within 1 min. Separation by microchip electrophoresis was compared to that by capillary electrophoresis, and the difference was discussed in terms of column efficiency and sample column capacity.