CuO-CeO2 catalyst precursors were synthesized by homogeneous thermal decomposition of urea. Catalysts containing different Cu/Ce ratios were obtained after calcination of the precursors at 450 degrees C and characterized by ICP-OES, N-2 adsorption, XRD and TPR. Catalytic tests were performed in the temperature range 100-300 degrees C to evaluate the activity of these samples for the COPROX reaction. A strong synergy between Cu and Ce is evidenced by the difference in the catalytic activity of the individual oxides (CuO and CeO2), a mechanical mixture of both oxides and a Cu-Ce mixed catalyst. The synergy between Cu and Ce is confirmed by the improvement of the reducibility of both cations in the mixed samples. Nitric acid and ammonium carbonate washed catalysts, especially high-copper-content samples, are more active than the untreated catalysts suggesting that the washing procedure could provoke a destruction of the polycrystalline structure that improves the contact between the reactants and the catalytic sites. (c) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.