The effect of the pre-treatment conditions on the evolution of gold species on an Au/TiO2 sample prepared by deposition-precipitation with urea has been followed by FF-IR spectroscopy of adsorbed CO. Gold is in the form of Au3+ species on the as-prepared sample and is not affected by evacuation at ambient temperature. However, the Au3+ species are readily reduced by CO at ambient temperature giving rise immediately to Au+ cations (the corresponding carbonyls displaying a hand at 2168 cm(-1)), which are then slowly converted into metallic gold (carbonyl hand at around 2106 cm(-1)). The Au3+ species are reduced to metal gold (respective carbonyl bands in the 2135-2100 cm(-1) region) when a fresh sample is heated at T >= 473 K. Water was found to affect CO adsorption on metal gold sites only slightly. Oxidation of Au-0/TiO2 by oxygen failed to produce cationic gold species. However, metallic gold was oxidized by heating the sample in a NO + O-2 mixture even at 573 K. (c) 2005 Elsevier B.V. All rights reserved.