Oxygen evolution by electrolysis of aqueous solutions has been studied on metallic conducting oxides, known as Magneli phases. The TinO2n-1 ceramic electrodes have been prepared by reduction of TiO2 compacts with hydrogen. The voltammetric behaviour before and after the electrode reaction was investigated and the response of the oxide surface to the anodic polarization was observed. The influence of porosity of the ceramic electrodes on the electrochemical reaction was examined using electrodes of different pore size distributions. The roughness factors of the electrodes were estimated utilizing cyclic voltammetry.