Drug residues have been detected in human hair specimens by a variety of analytical techniques. These reports have generated substantial interest in using hair as a historical record of drug usage. Current studies are designed to determine the presence and time course of drugs of abuse in human hair. Healthy male volunteers with a history of chemical substance abuse participated in the study. Informed consent was obtained and all procedures were approved by the hospital Institutional Review Board. Subjects resided on the clinical ward of the ARC. Head and facial hair specimens were obtained prior to and after administration of drugs of abuse. Blood, saliva and urine specimens also were obtained. Analyses of tissue and biofluids for drug was performed by radioimmunoassay and gas chromatography/mass spectrometry. These studies provide the scientific basis for determination of the usefulness of hair as a "historical record" for substance abuse.