The influence of incorporating MnO2 in Au/CeO2 catalyst on high selective oxidation of CO in hydrogen stream (PROX) reaction was studied. The presence of MnO2 increased the concentration of metallic Au species. The PROX reaction showed that the CO conversion of all samples increased with increasing reaction temperature, whereas the selectivity to CO oxidation decreased with the increasing reaction temperature. For Au on single oxide-support, Au/CeO2 showed a much higher CO conversion than Au/MnO2. However, the selectivity of Au/CeO2 decreased with reaction temperature significantly than Au/MnO2. This is an abstract of a paper presented at the 2006 AIChE Spring Annual Meeting (Orlando, FL 4/23-27/2006).