Sulphur doped nanoparticles of titanium dioxide were prepared by the reaction of titanium butoxide and thiourea in methanol. X-ray powder diffraction and High resolution transmission electron microscopy were used to investigate the crystallinity of the prepared nanoparticles. Based on the X-ray photoelectron spectroscopy measurements sulphur is present in the form of S6+ which substitutes Ti4+ in the titania lattice. The band gap energies of synthesised photocatalyst were calculated from the fitting of experimental dependences by double Boltzmann symmetrical functions. The photocatalytic activity of the samples was determinated by the measurement of the 4-chlorophenol (4-CP) degradation in the aqueous suspensions in the ultraviolet and visible region. Electron paramagnetic resonance spectroscopy confirmed the generation of (OH)-O-center dot radicals from S doped TiO2 under vis and UV irradiation. (C) 2010 Elsevier B.V. All rights reserved.