The electrochemical reduction of nitrite was studied at several electrode materials in 7.5 M sulfuric acid solutions. The thin oxide films on the noble metals, Pt, Ir and Rh, did not interfere with the reduction process. A thick oxide layer, as on Nb and Ta, however, did shift positively the reducing potential by several hundreds of mV. In these solutions, the protecting layer on a lead electrode (lead sulfate) behaved in the same manner. From the decrease in the current in repeated cyclic experiments, it could be concluded that poisoning of the active surface sites of the electrodes by oxygen did change the reduction mechanism of nitrite.