A capillary zone electrophoretic (CZE) method for the determination of rutin in an ethanolic extract of the aerial parts of Hypericrum perforatum (Hypericaceae) is described. The analysis was performed using a fused-silica capillary and a background electrolyte consisted of 10% ethanol and 20 mM berate buffer at pH 8.0 applied at a potential of 28 kV, vacuum injection of 1 s and detecting at 200 nm. Rutin had a migration time of 10.1 +/- 0.2 min. Reproducibility was 1.26% for 9.37x10(-5) iM standard rutin. Detection limit was 2.7x 10(-6) M (S/N = 3). A well-correlated calibration equation was obtained for the mentioned conditions. The amount of rutin in the total plant material was found to be 0.21% +/- 0.02.