Nanocrystalline Bi3TiNbO9 powders were synthesized by a sol-gel process, based on a colloid solution of bismuth acetate, titanium butoxide and niobium ethoxide. X-ray diffraction analysis revealed that pure Aurivillius phase of Bi3TiNbO9 could be prepared at a calcination temperature of 500 degrees C. By using scanning electron microscopy and gas adsorption method, the morphology and the specific surface area of the powders were examined. The photophysical properties of Bi3TiNbO9 were investigated by means of the UV-visible diffuse reflectance spectrum, from which a band gap similar to 3.2 eV was empirically calculated, The as-prepared Bi3TiNbO9 powders were applied in the photodegradation of organic contaminant for the first time, and they showed effective photocatalytic activity for the complete decomposition of methyl orange under UV light irradiation. (C) 2008 Published by Elsevier Ltd.