A method for the determination of 4,4'-methylenedianiline, aniline, o-anisidine, 3, 4-dimethylaniline, p-anisidine, 3-aminophenol, 1-naphthylamine in hair dyes was established by capillary electrophoresis coupled with field-amplified sample stacking. The optimum running buffer was an aqueous solution containing 0.15 mol/L NaH2PO4 and 0.015 mol/L trolamine (pH 2.3), and the baseline separation was achieved within 6.5 min. The effects of phosphoric acid and acetonitrile concentration in the sample matrix, the length of the preinjection water plug, and the sample injection voltage and time on the stacking efficiency were investigated. The optimum stacking conditions for the real samples included a water plug of 3.45 kPa (0.5 psi) x 6 s, the addition of 40% (v/v) acetonitrile and 0.6 x 10(-3) mol/L phosphoric acid to the sample solution and a sample injection of 10 kV x 10 s. The seven analytes all showed good linearities (R2 > 0.996) within 3 - 1 000 microg/L, with the detection limits in the range of 0.26 - 2.75 microg/L. The method was shown to provide over 1 - 3 magnitudes of sensitivity enhancement. 3-Aminophenol was found in two black hair dyes, and the amounts were 7.32 mg/g and 1.34 mg/g, individually. The recoveries ranged from 74% - 108%. The proposed approach may find widespread applications for the determination of trace aromatic amines and other cationic analytes in various sample matrixes.