A simple, sensitive and fast capillary electrophoretic method was optimized for the identification and determination of allelopathic phenolic compounds (vanillin, caffeic, 4-hydroxybenzoic, ferulic, salicylic, protocatechuic and 4-coumaric acids) in plant materials. Separation in an uncoated silica capillary (Supelco Select - FS75, effective length 22 cm, total length 31 cm, 75 mm I.D., 363 mm O.D.) was performed at 6 kV in 20 mmol/l boric acid and 60 mmol/l Na₂HPO₄ buffer (pH 8.75). The method was applied to the determination of vanillin, 4-hydroxybenzoic and protocatechuic acids in Ranunculus bulbosus, Veronica chamaedrys and Sanguisorba minor and in barley seeds. The results were in good agreement with those obtained by liquid chromatography.