Abstract: A reversed phase high performance liquid chromatographic method was de-veloped for the screening and simultaneous determinations of mixed benzodia-zepines involving Flurazepine,Nitrazepine,Clozapine,Estazolam,Oxazepine,Chlorodiazepoxide,N-desmethyldiazepine and diazepine in serum.Benzodiazepines in serum were extracted with dichloromethane at pH9.0,chromatographed on a NOVA-PAK C_(18)column(15cmx3.9mmID,5μ)anddetected at UV 240nm,the mobile phase was mathanol:water:acetonitril:HAc,TEMED(90:100:10:1:0.8),the relative retention data of henzodiazepines(inabove order)were 0.42,0.51,0.58,0.62,0.72,1,1.25 and 1.61 respectivily:chlorodiazepoxide was selected as an internal standard.Method characteristicssuch as linearity,reproducibility,specificity,minium determination level andrecovery were obtained.The relative retention data on the systems is considered with reference tothe problem of identifying unknown benzodiazepines,the presented methodprovided a new approach to forensic analysis of mixed benzodiazepines.This method had been applied by an emergency patient's serum specimenwho had ingested clozapine.