Chromium spinels (MCr2O4)-Cr-II (M-II = Co, Mn, Fe, Mg, Cu) of the same structure but different reducibility, were found new, promising supports for Au nanoparticles in oxidation of CO, including selective (preferential) oxidation in the presence of hydrogen. Oxidation of CO on Au/(MCr2O4)-Cr-II occurred already at room temperature, the activity depends on the nature of M-II (100% conversion of CO at 50 degrees C on Au/CoCr2O4 was observed). The activity in CO oxidation increases with the increasing reducibility of the supports and the catalysts, measured by H2TPR, and with the increasing potential of the M-II/M-III redox couple (for Co, Mn, and Fe spinels). This shows the role of the support redox properties in Au-based catalysts. In the presence of hydrogen (selective oxidation of CO), the catalysts are more active and show high (90-100%) selectivity to CO2. (c) 2005 Elsevier B.V. All rights reserved.