TiO2 (10 at.%)-doped WO3 thin films were deposited on ITO-coated glass substrates by spin-coating a peroxotungstic acid solution which was stabilized by the addition of Ti(OBun)(4). Effects of annealing temperature and water content on the electrochromic properties of the WO3-TiO2 films were investigated by cyclic voltammograms coupled with in situ monochromatic transmittance measurements. The poor electrochromic properties of the 350 degreesC-annealed films were found to have been largely improved by storing in air for 1 week, presumably due to the accelerating role of adsorbed water in the lithium insertion into the WO3-TiO2 films.