Results of these studies have shown that extractions with 0.1N HCl are efficient at removing the target compounds from hair and appear to be as effective as enzymatic digestions that dissolve the hair. GC/MS with either electron ionization or chemical ionization was found to provide accurate and unambiguous determinations of the target compounds. Tandem mass spectrometry (MS/MS) also provided accurate results when performed on extracts from hair, but results were ambiguous when MS/MS was performed on hair segments directly. Environmental issues, including the removal of powdered and vapor-deposited cocaine from the hair surface and the effect of various hair treatments on the levels of cocaine entrapped in hair, have also been investigated. Removal of cocaine deposited on hair was incomplete by all approaches tested, making differentiation of hair of cocaine users from hair with environmental exposure of cocaine difficult. Cocaethylene, a cocaine metabolite believed to be formed in the liver, was found in the hair of some cocaine users and may be a good marker for proving drug use. Common hair treatments, such as shampoos, conditioners, and peroxide bleaches, reduced cocaine levels in a fortified hair material by 60 percent to 80 percent after 30 treatments. Finally, to assist laboratories in evaluating the accuracy of their methods, two human hair reference materials with recommended concentrations of cocaine, benzoylecgonine, morphine, and codeine determined by GC/MS have been developed. 9 figures and 2 tables