Three benzodiazepine derivatives are currently indicated specifically for the treatment of insomnia in the United States. Flurazepam is biotransformed to at least two rapidly appearing and rapidly eliminated intermediate metabolites which probably contribute to sleep induction. The final metabolite, desalkylflurazepam, appears slowly, but has a long half-life ranging from 40 to 150 h. This metabolite accumulates extensively during multiple dosage. Temazepam is a slowly absorbed drug and has an intermediate half-life in the range of 10-20 h. Triazolam has an intermediate absorption rate, but is rapidly eliminated (half-life 1.5-5 h) making it essentially non-accumulating. Understanding of the pharmacokinetics of benzodiazepine hypnotics can contribute to understanding of their clinical properties.