Oxidation of CO was carried out at room temperature with the use of aqueous Solutions of polyoxometalates over carbon-supported g-old catalysts. The turnover frequency (TOF) for CO oxidation reaches high rates of 4.7 s(-1) for catalysts with average gold particle sizes of 5 nm, estimated by X-ray diffraction (XRD) and transmission electron microscopy (TEM), and with gold loading of 1 wt%. determined by elemental analysis. Lower rates are observed at higher gold loadings, which may be attributed to mass transport limitations in the present system and to the presence of larger gold particles. Carbon-supported gold catalysts exhibit selective oxidation of CO versus H-2, and a small increase in the selectivity for CO versus H-2 oxidation is observed as the gold particle size decreases from 12.1 to 5.6 run. (c) 2005 Elsevier Inc. All rights reserved.