CuO-CeO2 catalysts prepared by the urea gelation/co-precipitation (UGC) method were studied for the preferential oxidation of CO in H-2. The activity and selectivity of these catalysts are among the best reported to date for application to reformate-type gas mixtures. For a material calcined at 650 degreesC, similar to5 at.% Cu content is sufficient for maximum activity. Cu-O-Ce phases, comprising copper oxide clusters strongly associated with ceria, are proposed as the active sites for the reaction. No inhibition by CO2 is observed at temperatures above 140 degreesC, but the combined effect of H2O and CO2 is stronger, requiring operation at 165 degreesC for 99% CO conversion and 65% selectivity. (C) 2004 Elsevier B.V. All rights reserved.