A procedure is presented for simultaneous analysis of morphine, codeine, 6-monoacethylmorphine, methadone, cocaine, benzoylecgonine, ecgonine methylesther, cocaethylene, tetrahydrocannabinol, cannabidiol, and cannabinol, in hair, of drug of abuse, addicts. The method involves, decontamination in sodium dodecyl sulfate 1%, distilled water and methanol, pulverization in a ball mill,addition of deuterated internals standards, heat extraction in methanol. The extracts were evaporated to dryness and analyzed with gas/chromatography/mass spectrometry(GC/MS) before and after BSTFA/TMCS 1% silylation. The extracts were analyzed using electron impact GC/MS operating in SIM mode.