The performance of a PEM water electrolysis cell using IrxRuyTazO2 anode electrocatalysts has been examined. The oxide powders were synthesised using an aqueous hydrolysis method, followed by thermal oxidation. With the cell operating at 80 degrees C, the cell voltage at low current densities was dependant on the anode composition. At higher current densities the performance differences were less, most likely due to competing factors such as mass transport, electrical conductivity and surface area. A minimum in cell voltage was found at ruthenium contents around 40mol%, which is explained as being the optimum between specific activity and active surface area. Overall the best cell voltage we achieved was 1.567 V at 1 A cm(-2) and 80 degrees C, equating to an energy consumption of 3.75 kWh N m(-3) H-2 and an efficiency of 94% (epsilon(Delta H)). This was achieved using a Ir0.6Ru0.4O2 anode and 20% Pt/C cathode, with the total noble metal loading less than 2.04mg cm(-2). (C) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.