A high-performance liquid chromatographic rapid analytical method with β-naphthoquinone (BNQ) prelabelling for the simultaneous determination of methamphetamine (MA) and its metabolite, amphetamine (AP), in saliva has been studied. Without pretreatment, the direct derivatization of amphetamines in saliva has been developed. As a result of study on the optimization of the derivatization, a reaction mixture of 100μl of saliva containing MA and AP, 200μl of 0.5% Na₂CO₃, 200μl of aq. solution of 0.5% BNQ-sulfonate, 200μl of methoxyphenamine (1μg/ml) as an internal standard and 100μl of methanol, as a shift agent of interference peak was warmed at 40°C for 20 min. The reaction solution was extracted with n-hexane-ether (1 : 1) and the solvent was evaporated under N₂. The residue dissolved in acetonitrile was analysed by high-performance liquid chromatography on a column of μBondasphere C₁₈ with acetonitrilemethanol-0.01M H₂SO₄ (20 : 20 : 67) as a mobile phase (0.8ml/min) and electrochemical detection at -0V. Calibration curves were rectilinear for 50 to 10000ng/ml of MA and AP in saliva. By this method, 6 saliva samples of 4 male and 1 female human suspects who had taken i. v. dose of MA hydrochloride at 7.3, 7.8, 10.2, 20.4, 31 and 66.5h earlier were analysed to confirm the use of MA. Until at least 31h after use, MA and AP were detected at 0.1 to 24.8μg/ml. Comparing with urine and blood samples, the usefulness of the saliva sample was disccused.