The blood levels and the elimination kinetics of flurazepam and its major metabolites in blood were investigated in 10 volunteers after application of 60 mg flurazepam (Dalmadorm). Hydroxyethylflurazepam and desalkylflurazepam are the metabolites suitable for proving a previous flurazepam ingestion. Splitting of glucuronides is helpful for the determination of hydroxyethylflurazepam as the maximum blood concentration of the unconjugated metabolite does not exceed 1/3 of the concentration after glucuronidase splitting. Because of the different half-lives of formation and of elimination a characteristic time dependent pattern of flurazepam and its metabolites is observed in blood during 24 h after a single dosing. From this, conclusions may be drawn about the period of time between ingestion and sampling of the blood specimen. The accumulation of desalkylflurazepam is indicative of the dose applied or of previous multiple dosing. Parallel to the rise of the blood concentration of the metabolites the excretion of the corresponding hydroxyethylflurazepam glucuronide is detectable in urine. Within 30 min the concentrations are suitable for thin-layer chromatographic quantitation. An impaired performance of the volunteers was observed essentially during the absorption and the early distribution phase.