The apparent heterogeneous rate constants can be determined by a special cv technique in solutions containing both the oxidized and the reduced forms of a redox couple. The electrode materials are characterized by the difference between the k(ox)(0) and k(red)(0). The effect of RuO2/TiO2 ratio on the electrochemical effective surface area and the apparent rate constants of a redox system are investigated. The optimal composition of the RuO2/TiO2 electrode seems ta be in the 0.6-0.9 RuO2 mole fraction range.