The surface treatment of titanium dioxide (TiO2) powder using methacryloxypropyltrimethoxysilane (MCPTMS) has been carried out and the effects on the reduction of photocatalytic activity have been determined by the color change of the mixture of original and surface-treated powder with 1.3-butanediol after irradiation of ultraviolet light. From the results, surface modification of TiO2 with MCPTMS has been found to be effective in reducing its photocatalytic activity. Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), BET surface area measurements and CHN elemental analysis were used to characterize the modified particles. The effects of various factors, such as silane concentration. reaction temperature and time on the modifier grafting efficiency and photocatalytic activity were studied. (c) 2007 Elsevier B.V. All rights reserved.