The objective of this preliminary study was to determine whether hair can be used as an adjunct specimen for the monitoring of opiate use in a drug-treatment program. Subjects (n = 10) initiating clinical therapy for opiate addiction were monitored for up to 17 weeks with hair and urinalysis. Questionnaires were administered weekly to document hair cuts and chemical treatments. Hair specimens were collected weekly by cutting at the scalp and segmented into 1-cm lengths prior to analysis. Codeine (COD), morphine (MOR), and 6-monoacetylmorphine (6-MAM) concentrations in hair were measured by liquid chromatography-mass spectrometry (LC-MS) [limit of detection (LOD): 20 pg/mg for COD and 6-MAM; 50 pg/mg MOR]. Urine specimens were analyzed by semiquantitative radioimmunoassay (25-ng/mL cutoff) and LC-MS for codeine (COD), morphine (MOR), morphine-3beta-glucuronide (M3G), morphine-6 beta-glucuronide (M6G), and 6-monoacetylmorphine (6-MAM). The LOD and limit of quantitation (LOQ) in urine for COD, M3G, M6G, and 6-MAM were 10 ng/mL and 25 ng/mL for MOR. Interpretation of the segmental hair data in this study was complex and generally was not in agreement with urine data in most cases. Evaluation of hair data suggested that 6 of 10 subjects discontinued opiate use by the end of the study, whereas 3 of 10 appeared to have reduced their use. One subject appeared not to have used opiates throughout the entire study. In contrast, evaluation of urine data suggested that only 4 of 10 subjects significantly reduced use, and 6 of 10 continued drug use on at least an intermittent basis. Urine appeared to be a more sensitive indicator of changes in the pattern(s) of drug use during the course of clinical drug treatment.