The nucleation and growth of Au clusters supported on SiO2/Mo(1 1 0) has been studied by X-ray photoelectron spectroscopy (XPS), low energy ion scattering (LEIS), and temperature programmed desorption (TPD). Stoichiometric ultra-thin SiO2 films were synthesized and characterized by Auger electron spectroscopy (AES) and XPS. At 300 K, the growth mode of Au at fractional monolayer coverages is quasi-two-dimensional (2D); at higher coverages, three-dimensional (3D) growth was found with no evidence of a significant chemical interaction between gold and silica. Annealing Au/SiO2/Mo(1 1 0) to 1000 K led to sintering of the gold clusters. The desorption activation energies for Au coverages <0.2 monolayer equivalents were determined by TPD to be significantly lower than the sublimation energies found for higher coverages of Au clusters and for bulk gold.