These metabolites are excreted in hair after active cocaine administration; they predominated over all metabolites by a factor of 5-10. Two washing procedures to remove cocaine from environmentally contaminated hair were tested, but neither was completely successful in removing cocaine, suggesting that false positives can result from environmental contamination. Analysis of the methanolic wash of cocaine users' hair showed the presence of cocaine metabolites, suggesting that washing removes cocaine from the interior and exterior surfaces of hair during decontamination procedures. While the presence of cocaine, benzoylecgonine, and ecgonine methyl ester could be explained by environmental contamination with subsequent hydrolysis, the presence of either norcocaine or cocaethylene in an individual's hair seems to constitute evidence of internal cocaine exposure. 3 figures, 3 tables, and 16 references