The selective oxidation of CO in the presence of excess H-2 was investigated over a ceria-promoted Cu-alumina catalyst. This catalyst shows nearly exclusive oxidation of CO versus H, with an O-2 concentration in stoichiometric proportion to CO, making it possible to purify a fuel cell feed stream with a minimum loss of energy content associated with H, The effect of the presence of CO2 and H2O in the feed on the activity and selectivity of the catalyst, and the long-term stability were also investigated. The catalysts were characterized by X-ray diffraction (XRD), CO chemisorption and temperature-programmed reduction (TPR). Copper is better dispersed on the ceria-promoted alumina support in comparison to alumina alone. CuO is the active phase for selective CO oxidation. Oxygen vacancies supplied and enhanced by ceria are responsible for improved activity. (c) 2005 Elsevier B.V. All rights reserved.