It is necessary to extend the absorption range of TiO2 based materials from the ultraviolet to the visible light region for most photo-catalytic applications of TiO2 under solar irradiance or indoor lighting. Also, the ability to control the structural evolution, particularly the competition and transformation between different phases (anatase or rutile), is extremely important for the preparation of high efficiency TiO2 based photo-catalysts. In this work, we have systematically studied the effects of various processing factors on the phase selection process/outcome of nanocrystalline Fe-doped TiO2, which includes the level of doping ions, annealing temperature, solution pH and the addition of acidic anions, using a low temperature hydrothermal method. Both Fe-doped rutile and anatase TiO2 phases were obtained via varying the processing conditions. The visible-light photo-catalytic activity of doped materials was significantly improved over that of the pure TiO2 nanopowders, which was demonstrated by effective degradation of methylene blue under visible light. (C) 2010 Elsevier Ltd. All rights reserved.