The analysis of hair for drugs of abuse reveals information regarding past drug exposure. We developed methods for washing, extraction and analysis of hair samples for cocaine, heroin and metabolites. Twenty paired head- and arm-hair samples, collected from known heroin/cocaine abusers, were analyzed with a new comprehensive GC/MS assay for cocaine, heroin and metabolites. Cocaine and 6-acetylmorphine (6-AM) were the major analytes present in both head- and arm-hair samples. Cocaine was detected in all head- and 17 arm-hair samples. The concentration of cocaine found was 4-760 ng/10 mg in head hair and 0-1090 ng/10 mg in arm hair. Less benzoylecgonine was present in a concentration range of 0-158 ng/10 mg of head hair and 0-125 ng/10 mg of arm hair. Heroin was found in only 2 head-hair samples, whereas 6-AM was present in 14 head and 6 arm-hair samples. The concentration of 6-AM was 0-8 ng/10 mg in head hair and 0-31 ng/10 mg in arm hair. Morphine was present in 3 head-hair samples in a range of 2-9 ng/10 mg and was not detected in arm-hair samples. When results were compared by groups (head hair versus arm hair, Caucasoid versus Africoid), only two significant differences were found. Cocaine concentrations in both head and arm hair were significantly (P < 0.05) higher in the Africoid group than in the Caucasoid group. The reasons for these differences were not readily apparent, but could have been due to differences in the level of cocaine use or to ethnic differences in the deposition of drug in hair.