A high and stable activity for gold/ceria catalyts has been established for the water-gas shift reaction. The relationship between gold loading and catalytic activity was studied over a wide temperature range. The influence of space velocity and H2O/CO ratio at different temperatures on the catalytic activity and stability was also investigated. The reduction/oxidation processes of ceria in the presence of gold was readily followed by TPR measurements. It was shown that ceria plays the role of an active support capable of producing oxygen. The high and stable activity of gold/ceria catalysts could arise from the high and stable gold dispersion present during the catalytic operation.