TiO2 materials possessing not only photocatalytic but also electrochromic properties have attracted many research and development interests. Though WO3 exhibits excellent electrochromic properties, the much higher cost and water-sensitivity Of WO3 as compared with the TiO2 may restrict the practical application Of WO3 materials. In the present study, the feasibility of preparing nanocrystalline porous TiO2/WO3 composite thin films was investigated. Precursors of sols TiO2 and/or WO3 and polystyrene microspheres were used to prepare nanocrystalline pure TiO2, WO3, and composite TiO2/WO3 thin films by spin coating. The spin-coated thin films were amorphous and, after heat treating at a temperature of 500 degrees C, nanocrystalline TiO2, TiO2/WO3, and WO3 thin films with or without pores were prepared successfully. The heat-treated thin films were colorless and coloration-bleaching phenomena can be observed during cyclic voltammetry tests. The heat-treated thin films exhibited good reversible electrochromic behavior while the porous TiO2/WO3 composite film exhibited improved electrochromic properties. (c) 2005 Elsevier B.V. All rights reserved.