SBA-15 functionalization with 3-mercaptopropyltrimethoxysilane was used to prepare a supported gold catalyst for the low temperature CO oxidation reaction. Catalytic runs were performed at atmospheric pressure and T = 40-150 A degrees C and the influence of different thermal treatments of the sample prior to reaction was studied. The modifications induced by the pre-treatments in the physico-chemical properties of both the carrier and the disperse phase were investigated by chemical analysis, CHS elemental analysis, N-2 adsorption-desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), solid state cross-polarization magic-angle-spinning nuclear magnetic resonance spectroscopy (CPMAS NMR) of Si-29 and C-13 and Fourier transform infrared spectroscopy (FTIR). The pre-treatment conditions were found to strongly affect both the gold particle size and the nature of the Au surface species. An appreciable catalytic activity was found on samples treated at 600 A degrees C in H-2/He atmosphere, provided that the functionalizing agent had been completely removed by a previous high-temperature calcination.