Antimony-platinum doped tin dioxide electrodes supported on titanium have been prepared by thermal decomposition. The effect of the progressive replacement of Sb with Ru (x = 0.00; 3.25; 6.50; 13.00 at.%) on their electrochemical response in acid medium has been analysed by cyclic voltammetry. The morphology of the coatings was observed by scanning electron microscopy. Ti/SnO2-Sb-Pt electrodes without Ru presented a cracked-mud structure, typical of oxide electrodes prepared by thermal decomposition. The introduction of Ru in the oxide layer modified the coating morphology. The roughness increased and passed through a maximum with the increase of Ru content. A relation between the surface morphology, the roughness factor, voltammetric charge and the electrochemical activity has been established. The mechanism and electrocatalytic activity towards the oxygen evolution reaction has been studied from Tafel measurements. The progressive introduction of Ru in the electrodes increased their electrocatalytic activity for the oxygen evolution reaction with a change on the mechanism from non-active to active electrodes. The electrocatalytic activity mainly depends on electronic factors. (C) 2009 Elsevier Ltd. All rights reserved.