A fast micellar electrokinetic chromatography (MEKC) method for simultaneous assay of aesculin, aesculetin, and phenylephrine was developed and validated. The separation was carried out in a fused-silica capillary (50 mu m id, total length 64.5 cm, effective length 8.5 cm) with UV detection at 210 nm, temperature 25 degrees C and separation voltage -25 kV. The samples were loaded hydrodynamically at a pressure of -50 mbar for 6 s. The background electrolyte of pH 8.6 contained 20 mM boric acid, 60 mM SDS, and 5% (v/v) of methanol. The calibration curves were linear in the range 10-500 mu g/mL for aesculin and aesculetin and 12.5-625 mu g/mL for phenylephrine. The RSD values of corrected peak areas were 0.6-1.2% (n = 6) when determining 0.2 mg/mL of aesculin and aesculetin and 0.25 mg/mL of phenylephrine in prepared standard mixtures. The method was successfully applied to the assay of aesculin and phenylephrine in a pharmaceutical preparation (RSD = 1.9-2.0%; n = 3) and the robustness of the method for both, the determination of analytes and the system suitability test parameter values, was evaluated with the use of Plackett-Burman design.