A method for preparing a cation exchange membrane, comprising the introduction of an organic polymer having sulfonic acid groups and of finely disperse electrically conductive particles of a catalyst material into a liquid phase, the resulting suspension being used to coat a foil of a cation exchange material on at least one side, wherein the organic polymer having sulfonic acid groups is soluble in an aprotic polar solvent and contains units of the formulae (Ar1X) and (Ar2Y) which are at least partially substituted by sulfonic acid groups, Ar1 and Ar2 being identical or different bivalent arylene radicals, X being oxygen or sulfur and Y being a carbonyl radical, sulfoxide radical or sulfonyl radical and said material being dissolved in a solvent, a finely disperse electrically conductive catalyst material being suspended in the solution and this suspension being used to coat a foil which contains a polymeric cation exchanger having sulfonic acid groups and the coating which still contains solvent being treated with a liquid which is miscible with the solvent, but in which the dissolved cation exchange material is insoluble, so that pores are formed in the top layer of the membrane.