Alumina was incorporated with the solid solutions of CexZr1-xO2 to form CexZr1-xO2-Al2O3 mixed oxides, by the suspension/co-precipitation method. to be used as supports of CuO/CexZr1-xO2-Al2O3 catalysts. They were characterized, and the effects of Al2O3 on the selective oxidation of CO in excess hydrogen were examined. Incorporating Al2O3 increased the dispersion of CexZr1-xO2, but did not change their main structures and did not weaken their redox properties. Doping zirconium into CeO2 increased the mobility of lattice oxygen and enhanced the activity of the 7%CuO/Ce0.9Zr0.1O2-Al2O3 catalyst in the selective oxidation of CO in the H-2-rich feed. The promotion of CO oxidation became weaker as the fraction of Zr4+ dopant increased above 0.1. A small amount of Zr4+ dopant and an appropriate amount of incorporated Al2O3 could obtain a good candidate such as 7%CuO/Ce0.9Zr0.1O2-Al2O3(20%) for a preferential oxidation (PROX) unit in a polymer electrolyte membrane fuel cell system for removing CO. Its activity was comparable with, and its selectivity was much larger than, that of the noble catalyst 5%Pt/Al2O3. (C) 2007 Intemational Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.