The electro-oxidation of p-methoxytoluene (p-MT) at the graphite/Nafion composite electrodes was investigated, p-Methoxybenzaldehyde (p-MBA) and a small amount of p-methoxybenzoic acid (p-MBAc) are obtained through preparative electrolysis of p-MT. There is slightly higher current efficiency at the composite electrode employing a Ce3+-Nafion membrane than at that employing a H+-Nafion membrane at low current densities.The electrochemical oxidation of p-MT is mainly a four-electron oxidation process controlled by the diffusion of some species. (C) 1998 Elsevier Science Ltd. All rights reserved.