Abstract: A porous high surface area composite electroconductive catalytic material, particularly as electrocatalyst for electrolysis electrodes, comprises a porous pre-formed matrix which is a catalytic mixed crystal material of at least one platinum group metal oxide and at least one valve metal oxide throughout which a subsequently-added additional catalyst preferably consisting of at least one platinum group metal and/or oxide is dispersed by chemideposition in an oxidizing or reducing atmosphere preferably followed by an annealing post heat treatment. The porous matrix may be ruthenium-titanium oxide and the additional catalyst advantageously comprises at least two oxides of ruthenium, rhodium, palladium and iridium, other combinations being possible.