Over the past decade, several methods for analyzing hair for cocaine have been developed, and laboratories throughout the world are conducting such tests. No single method or combination of methods has been accepted as a benchmark or standard. Because so many methods have been used, some specific and some nonspecific, it is difficult to compare many of the data, and serious questions still remain about how to interpret the results of a hair test for cocaine. Still, there is a current body of knowledge about cocaine hair analysis. In humans and experimental animals, cocaine ingestion can be detected by analyzing hair (or fur). Even a single dose of cocaine can be detected if sensitive methods are used. Increasing doses usually result in increased levels of the drug and metabolites in hair; however, a clear dose-response relationship has not been established. At the very least, it is known that the pharmacokinetics of cocaine incorporation into hair do not mirror its pharmacokinetics in plasma, because cocaine is the major analyte in hair, and metabolites BZE and EME are present in low and variable amounts in hair. Hair sampling procedures are becoming more standardized, but the effectiveness of washing procedures in removing cocaine adsorbed or incorporated from the external environment remains controversial. 44 references and 3 tables