Tungsten oxide is a widely used electrochromic material for smart windows. In order to study the charge carriers involved in the electrochromic process, it is important to characterize the electrical transport in tungsten oxide. Substoichiometric amorphous tungsten oxide films were prepared by DC-magnetron sputtering. The films were electrochemically intercalated with lithium. The Li/W intercalation ratios for the tungsten oxide films were in the range 0.15-0.53. Temperature dependent resistivity measurements were performed in the temperature range 77-300 K for samples at different lithium intercalation levels. It was found that the data are consistent with the variable range hopping model. (C) 2004 Elsevier B.V. All rights reserved.