A simple determination method of amphetamine (AP) and methamphetamine (MA) in human blood was developed using on-column derivatization and gas chromatography-mass spectrometry (GC-MS). AP and MA were adsorbed on the surface of Extrelut and then derivatized the N-propoxycarbonyl derivatives using propylchloroformate. Pentadeuterated MA was used as an internal standards. The recoveries of AP and MA from the spiked blood were 89.7 and 90.3%, respectively. The calibration curves showed linearity in the range of 12.5-2000 ng/g for AP and MA in blood. The coefficients of variation of intraday and interday were 0.42-4.58%. Furthermore, this proposed method was applied to some medico-legal cases of MA intoxication. MA and its metabolite AP were detected in the blood samples, and the correlation of the blood level of amphetamines and the behaviors of the victims was in good agreement with the criteria proposed by Nagata [Jpn. J. Legal Med. 37 (1983) 513].