AbstractMass spectra and gas chromatographic data are presented for flurazepam and its metabolites; monodesethyl flurazepam, didesethylflurazepam, hydroxyethylflurazepam,N1‐desalkylflurazepam,N1‐desalkyl‐3‐hydroxy flurazepam, and flurazepam‐N1‐acetic acid. The on‐column thermal degradation of didesethylflurazepam,N1‐desalkyl‐3‐hydroxyflurazepam and flurazepam‐N1‐acetic acid is reported and discussed. Mass spectrometric and gas chromatographic data are also presented for the benzophenones obtained by acid hydrolysis of flurazepam and its metabolites. The occurrence of flurazepam metabolites in urine from five forensic cases after various treatments has been investigated. A possible new ‘metabolite’ of flurazepam was det