A series of AuPt/A zeolite and Pt/A zeolite catalysts prepared by incipient wetness impregnation are investigated for the preferential oxidation (PROX) of carbon monoxide in the presence of hydrogen over the temperature range of 50-310 degrees C under atmospheric pressure. The results indicate that when a small amount of gold is added to the Pt/A zeolite catalyst, the CO selectivity is improved at low temperatures, and 1 % AuPt/A zeolite (at a weight ratio of Au:Pt = 1:2) gives the best performance, which provides a high CO conversion in combination with a high CO selectivity. In more realistic simulated reformate gases containing 10% CO2 and 10% H2O, there is not much difference between those in the presence and the absence of CO2 and H2O. Transmission electron microscopic and X-ray diffraction studies show that the two metals, An and Pt, appear to be severely phase separated, which is confirmed by energy dispersive investigations. (c) 2007 Elsevier B.V. All rights reserved.