In this paper we report a kinetic study of the electro-oxidation of hydrazine catalyzed by vitamin B-12 pre-adsorbed on an ordinary pyrolytic graphite electrode. Kinetic parameters Were determined by linear sweep voltammetry and rotating-disk electrode polarization curves. The order of the reaction is 1 in OH- ions and Tafel plots give slopes of 80 mV/decade. A possible redox-catalysis mechanistic scheme is proposed.