The voltammetric behaviour of three 5-nitroimidazoles, metronidazole, tinidazole and ornidazole, was investigated, and a method was developed for the simultaneous determination of these compounds, based on their reduction at a hanging mercury drop electrode (HMDE) in pH 8.95 buffer with differential pulse voltammetric (DPV) approach. Well defined voltammetric waves with peak potentials of -692, -640 and -652 mV were observed for these compounds, respectively. It is difficult to determine them individually from their mixtures without preseparation, for their voltammetric peaks overlapped seriously, so the chemometrics were used to resolve the overlapped voltammogram and quantify the mixtures. The proposed method was successfully applied to the determination of three 5-nitroimidazoles in milk and honey samples.