A procedure is presented for the simultaneous identification and quantification of amphetamine (AP), methamphetamine (MA), methylenedioxyamphetamine (MDA) and methylenedioxymethamphetamine (MDMA) in human hair. The method involves decontamination of hair with dichloromethane and warm water, heat-alkaline hydrolysis in the presence of deuterated internal standards, liquid-liquid extraction and gas chromatography-mass spectrometry after derivatization with pentafluoropropionic anhydride-pentafluoropropanol. The limit of detection for AP, MA and MDA was 0.05 ng/mg using a 50-mg hair sample; for MDMA it was 0.1 ng/mg. Coefficients of variation ranged from 7 to 18%. This assay has been successfully utilized in the evaluation of the deposition of the drugs in hair obtained from various parts of the anatomy of a stimulant abuser.