A method is developed and validated for analysis of the antibiotic cefadroxil using micellar electrokinetic capillary chromatography. It permits cefadroxil to be completely separated from ten of its known related substances within 15 min (including the washing procedure). The separation is performed in an acetate buffer (50 mM, pH 5.25) containing sodium dodecyl sulfate (SDS; 110 mM). The fused-silica capillary was 44 cm long (36 cm effective length), 50 microm ID; the voltage, 18 kV; temperature, 15 degrees C; and the detection wavelength; 254 nm. The influence of the type of buffer, buffer pH and concentration, and of the SDS concentration was investigated. The robustness of the method was examined by means of a full-fraction factorial design. The parameters for validation such as linearity, precision, limit of detection and limit of quantitation are also reported.