A simple and rapid method for analysis of methamphetamine (MA) and amphetamine (AP) in blood was developed using head space-solid phase microextraction (HS-SPME) and gas chromatography-mass spectrometry/electron impact ionization-selected ion monitoring (GC-MS/EI-SIM). A vial containing a blood sample, sodium hydroxide, and pentadeuterated methamphetamine as an internal standard, was heated at 80 degrees C for 20 min. The extraction fiber of the SPME was exposed for 5 min in the head space of the vial. First, heptafluorobutyric anhydride solution was injected into the injection port of the GC-MS to make heptafluorobutyramide (HFB) derivatives of amphetamines, and compounds absorbed on the fiber were detached by exposing the fiber in the injection port. Straight calibration curves of MA and AP were obtained from 0.01 to 2 micrograms/g in blood, respectively. No interfering substances were found, and the time for analysis was 30 min for one sample.