The electrocatalytic hydrogenation of m-xylene (1,3-dimethylbenzene) was investigated at room temperature in 0.5 M H2SO4 solutions on a platinized-platinum (Pt/Pt) electrode. It was found that the hydrogenation process of m-xylene took place only in the potential region corresponding to the weakly adsorbed hydrogen (0 < E-H < 0.25 V) and that the electrocatalytic activity of the Pt/Pt electrode was dependent on the hydrogenation potential. The hydrogenation of m-xylene yielded steroisomeric product mixtures of the saturated 1,3-dimethylcyclohexane (1,3-DMCH), cis- and trans-1,3-DMCH. The cis/trans isomer ratio was found to be strongly dependent on the potential on which the hydrogenation of m-xylene has been carried out. These results were compared with those reported for the gas and liquid-phase catalytic hydrogenation of m-xylene and explained through a model of molecular reorientation dependent on the electrode potential.