Nanometer sized metal clusters dispersed on oxide supports often exhibit much higher activity than single-component metal catalysts. Their catalytic performance markedly depends on cluster size, shape and size distributions, along with support materials and support preparation methods. Supported metal nanoclusters can also easily rearrange and sinter during the course of thermally activated catalytic reactions even at moderate temperatures. An accurate assessment of the effects of cluster-support interactions on the growth, structure and reactivity of supported metal clusters, as well as the adsorbate-induced structural changes is therefore necessary to understand their catalytic performance under realistic operating conditions. The detailed understanding will also contribute to development of a new and reliable way to control their structural catalytic properties on the atomic scale. As a part of the effort to gain this atomic level understanding, we present our recent findings from density functional theory calculations, including: electronic structure of a reduced TiO2(1 1 0) surface and interactions between oxygen vacancies, with a brief introduction to the dynamics of oxygen molecules on the reduced surface, role of oxygen vacancies and oxygen adspecies in the nucleation of Au, Ag and Cu clusters. (c) 2005 Elsevier B.V. All rights reserved.