Photocatalytic degradation of Direct Red 23 (DR23) by nano-Ag doped TiO2 has been investigated under different conditions. Photodeposition of 1.5% Ag on the surface of TiO2 enhanced its photoactivity in DR23 degradation. Optimal experimental conditions on catalyst amount, pH and dye concentration have been determined. Addition of some inorganic oxidizing species such as H2O2, (NH4)S2O8 and KBrO3 up to a certain concentration increased the rate of degradation. The higher photoactivity of Ag-TiO2 than TiO2 under UV irradiation can be ascribed to the effect of silver deposits acting as electron traps on the Ag-TiO2 surface. (c) 2008 Elsevier B.V. All rights reserved.