RuO 2 Re 2 O 3 /Ti (Ru:Re 7:3) electrodes prepared from the thermal decomposition of RuCl 3 and ReCl 3 were much more porous than conventional RuO 2 /Ti electrodes. Porosities of the RuO 2 Re 2 O 3 /Ti electrodes depended on the ionic radii of the rare earth ions. Rare earth ions added to electrodes to prepare the RuO 2 Re 2 O 3 /Ti electrodes were completely dissolved in the acid solution. After dissolution of the rare earth ions, the voltammetric charges of the resulting RuO 2 /Ti electrodes were still large. Rare earth chlorides were effective as pore initiators in preparing porous RuO 2 /Ti electrodes, and were recovered after the preparation as catalysts.