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A quantitative analytical procedure for the determination of benzodiazepines and metabolites in hair has been developed and validated. The hair samples were washed, incubated, and any drugs present were quantified using mixed mode solid-phase extraction and liquid chromatog-raphy with tandem mass spectrometric detection (LC/MS/MS) in positive electrospray ionization mode. The liquid chromatography is carried out on a ZORBAX Rapid Resolution High Throughput (RRHT) C18 column, which has a 1.8-µm particle size. For confirmation, two transitions were monitored and one ion ratio was determined, which was within 20 % of that of the known calibration standards. The range of concen-tration analyzed for each compound was 50 to 1,000 pg/mg hair. The intra-day precision of the assays at 100 pg/mg (n = 5) was as low as 1.75 % for 7-aminoclon-azepam, and as high as 11.8 % for a-OH-alprazolam. Inter-day precision (once each day for five days) ranged from as low as 2.55 % for diazepam to as high as 13.4 % fo