PbO2 + RuO2 composites have been electrodeposited onto Au rotating disc electrodes from suspensions of RuO2 in a mildly acidic lead nitrate + lead acetate electrolyte. These electrodeposits are stable at open circuit in H2SO4 solution, but not in acids, forming soluble Pb(II) salts. Tested as anodes for oxygen evolution from 0.5 mol 1(-1) H2SO4 at room temperature, PbO2 + RuO2 composites exhibit fairly high catalytic activity with an overpotential of 250 mV at 100 mA cm(-2) and a Tafel slope (slightly higher than 60 mV) close to that of stoichiometric RuO2 crystals. Their service life is limited, as observed previously for thermally prepared Ti/RuO2 films. Longer service life is shown by composite electrodes in which RuO2 is replaced with a mixed oxide of Ru and Sn.