The rate and mechanism of the electroreduction of chlorine on electrochemically oxidised Pt and Ru electrodes has been investigated relative to the state of oxide formation. Current/potential curves for the reduction process in 1 M HCl solution saturated with Cl-2 have been obtained for electrode surfaces in various states of preoxidation with the use of the rotating disc electrode technique (RDE). In the case of chlorine reduction on platinum, the results indicate that adsorption of chlorine molecules with a subsequent rate determining electrochemical adsorption step is the dominant mechanism. The exchange current density seems to decrease linearly with the logarithm of the amount of surface oxide. Chlorine reduction on ruthenium is best described by a Heyrovsky-Volmer mechanism with the first charge transfer reaction as the rate determining step. The Krishtalik mechanism incorporating adsorbed O.Cl+ intermediates is also able to describe the reaction successfully. The reaction order is constant for all oxide coverages while the exchange current density apparently moves through a maximum at intermediate oxide coverages (similar to100 mC cm(-2)). The results show that the electrocatalysis of the cathodic reduction of chlorine is very sensitive to the state of the oxide film on the surface. (C) 2004 Elsevier Ltd. All rights reserved.