Enhanced currents observed for reduction of methyl viologen cation radicals at zeolite Y-modified electrodes are due to conproportionation reactions. These occur between methyl viologen dications and zerovalent methyl viologen (MV0) deposited on the electrode surface. Double potential step chronocoulometry (DPSC) confirms that the presence of adsorbed MV0 on the conductive portion of the electrode. Moreover, in the presence of a surfactant, DPSC shows that the adsorbed phase dissolves with a reduction in the significance of conproportionation. Electron transport is unequivocally occurring outside the zeolite network because of the size and charge rejection of the anionic surfactant. Electrolyte cation-induced changes in the modified-electrode response are discussed in terms of ion exchange rates, and deposition-dissolution effects.