TiO2 doped WO3 thin films were deposited onto glass substrates and fluorine doped tin oxide (FTO) coated conducting glass substrates, maintained at 500 degrees C by pyrolytic decomposition of adequate precursor solution. Equimolar ammonium tungstate ((NH4)(2)WO4) and titanyl acetyl acetonate (TiAcAc) solutions were mixed together at pH 9 in volume proportions and used as a precursor solution for the deposition of TiO2 doped WO3 thin films. Doping concentrations were varied between 4 and 38%. The effect of TiO2 doping concentration on structural, electrical and optical properties of TiO2 doped WO3 thin films were studied. Values of room temperature electrical resistivity, thermoelectric power and band gap energy (E-g) were estimated. The films with 38% TiO2 doping in WO3 exhibited lowest resistivity, n-type electrical conductivity and improved electrochromic performance among all the samples. The values of thermoelectric power (TEP) were in the range of 23-56 mu V/K and the direct band gap energy varied between 2.72 and 2.86 eV. (c) 2005 Elsevier B.V. All rights reserved.