The study attempted to improve the reliability of discrimination (or identification) of dyed hair by analyzing chemical substances present in the hair, as an addition to the conventional macroscopical and microscopical examinations and ABO blood group examination. Oxidation hair-dye components were selected as the object of study. After alkaline-digestion, hair samples were adjusted to a pH of 12.6 to 12.8 and applied onto an Extrelut column. After 15 minutes, the components were simultaneously extracted and derivatized with n-hexane including 1 percent heptafluoro-n-butyryl (HFB) chloride. Their HFB derivatives within a condensed sample were diluted in ethyl acetate and analyzed by gas chromatography-mass spectrometry (GC/MS) with full mass scanning or selected ion monitoring. For estimating the levels of hair dye components, 2,4,6-trimethylaniline was used as the internal standard. Four of the components were detectable at 6 mg, one at 8 mg and one at 4 mg. Recovery percents using this procedure ranged from 54 to 86 percent. Tables, figures, references