The electrochemical behaviours of 2,2′-bipyridine-1-oxide, 2,2′-bipyridine-1,1′-dioxide, 4,4′- dihydroxy-2,2′-bipyridine-1,1′-dioxide and orellanine (3,3′,4,4′-tetrahydroxy, 2,2′-bipyridine-1,1′-dioxide) are described. Compounds characterized by two electrophores (bipyridine and N-oxide functions) are found to be electroreducible in an aqueous Britton—Robinson buffer. Direct current and differential pulse polarographic data are presented for reduction at the dropping mercury electrode at different pH values. In order to complete this study, the irreversibility of the reduction is established by cyclic voltammetry and the total number of electrons transferred is calculated from the controlled potential macroelectrolysis data. Two electrons are involved in the reduction of every N-oxide function. Both N-oxide functions are reduced simultaneously in the diamine oxides. In the case of orellanine, a proton reduction with a catalytic process connected with the reduction of the N-oxide functions is observed. Reduction products are identified. A relationship between structure and electroactivity is discussed. The toxicity of orellanine is examined in terms of oxido-reduction. Experimental parameters for the optimal quantitative determination of orellanine in biological fluids are determined: pH 2.3 and low concentration (between 10 t-7 and 10 t-6 M) in order to avoid strong adsorption phenomena.