The oxidation of CO was studied over a Au/TiO2 reference catalyst in a static reactor coupled to a thermodesorption device. The optimal vacuum activation/regeneration temperature is in the range 350-400 degrees C. The catalyst partly deactivates during the first runs, possibly through poisoning of the active sites by carbonate-like species, whose formation is clearly evidenced. Although a postreaction treatment under pure hydrogen is ineffective toward regeneration, the catalyst gradually recovers its initial activity for CO conversion in the presence of a low amount of hydrogen within the reactant mixture. Increasing the hydrogen pressure only promotes the oxidation of hydrogen, thereby decreasing selectivity in the preferential oxidation of CO. Consequently, we show that hydrogen-induced promotion of Au/TiO2 is a regeneration effect involving removal of carbonates rather than a boosting effect via new CO oxidation pathways. (c) 2006 Elsevier Inc. All rights reserved.