The effect of the addition of Triton x-100 on the electrochemical oxidation of 2-mercaptopyridine N-oxide (NOS) on mercury electrodes in aqueous solutions is investigated. The shape of de polarograms changed, (the prewave observed in the absence of Triton is now absent) and the de polarographic data conform with the oxidation mechanism previously proposed. The differential pulse polarographic data and the cyclic voltammetric data were explained on the basis of a reorientation of the radical NOS adsorbed on the mercury surface, directed by the electrode potential. The Gibbs free enthalpy of the reorientation process was found to be around 3.6 kJ mol(-1).