We present a small review of recent density-functional-theory (DFT) studies of the reactivity towards CO oxidation of supported Au nanoparticles. The possible structure of the periphery of the interface between a An particle and an oxide support is discussed. A certain structure, in which low coordinated Au atoms are overhanging the support without binding directly to the oxide atoms, is argued to be prototypical of medium-sized Au particles. This structure is shown to be particularly active both at the edges and at the comers of Au particles. Examples from the literature of Au systems supported on MgO(1 0 0) and rutile-TiO2 (1 1 0) are reviewed and new data are given for the reactivity of facet, edge, and corner sites of a Au-34 cluster supported on MgO(1 0 0). On the non-reducible oxide support, MgO(1 0 0), the CO oxidation is found to occur via CO adsorption to the Au particles and subsequent CO-promoted O-2 capture and formation of a CO center dot O-2 reaction intermediate complex. On the reducible oxide support, TiO2 (110), the O-2 is found to adsorb independently of the CO. However, on this support, the reaction still proceeds via CO center dot O-2 formation rather than via O-2 dissociation. (c) 2005 Elsevier B.V. All rights reserved.