The electrocatalytic activity of ternary oxides of nominal composition Ru0.3PtxTi(0.7-x)O-2 was investigated over the whole composition range using chlorine evolution as a model reaction. Composition was changed in 10 mol.% steps and the surface was characterized in situ by cyclic voltammetry (cv). Surface properties are governed by the RuOx features at low PtOx content (< 30%), while at higher PtOx content they are controlled by PtOx. A single Tafel line of 31 +/- 1 mV slope was observed at all compositions. The reaction order is zero with respect to H+ and 1.5 with respect to Cl-. At high PtOx content and low Cl- concentration (<1 mol dm(-3)) O-2 formation appears to control the gas evolution process. An inhibition of Cl-2 evolution is observed for PtOx greater than or equal to 30mol.%. On the whole, morphological effects predominate over electronic effects.