A study is presented for the separation and determination of fifteen 1,4-benzodiazepine drugs and metabolites by capillary electrophoresis (CE) compared with high-performance liquid chromatography (HPLC). A comparison is made between the CE determination of the compounds by conventional UV detection and LC determination with electrospray ionisation (ESI) ion-trap mass spectrometry. CE is shown to provide superior separation to HPLC but the MS-MS capability of the ion-trap allows for the specific detection and determination of four of the compounds, diazepam, N'-desmethyldiazepam, oxazepam and temazepam in the hair of a patient under clinical treatment with diazepam and temazepam. Selected mixtures of drugs and metabolites are determined by CE and LC and the determination of diazepam and its metabolites by CE-UV-ESI-MS-MS is also presented.