Surface modification of rough, high-surface area, nanocrystalline titania thin-film photocatalysts was performed by gold deposition via electron beam evaporation, with an attempt to enhance the decomposition reaction rate of industrial water pollutants. The materials were characterized and their photocatalytic activity was tested for methyl orange photodegradation. The surface deposition of gold particles improves the photocatalytic efficiency of the titania films by the synergetic action on the charge separation process onto the semiconductor. The most advantageous surface concentration of gold particles in the composite Au/TiO2 photocatalyst was found to be 0.8 mug cm(-2), leading to a two times faster degradation of methyl orange with respect to the rate obtained with the original TiO2 material. Higher surface loadings result in an efficiency decrease, and this can be understood in terms of an optimum gold particle size and surface characteristics as well as the semiconductor availability for light absorption and pollutant adsorption. No deactivation of the catalyst was observed after five consecutive photocatalytic experiments of new added pollutant. (C) 2003 Elsevier Inc. All rights reserved.