WO3-x nanorods were grown on the tips of electrochemical etched W filaments by in-situ heating under different growth conditions. This kind of nanorods has the average diameter of 20 nm and the length of 1-2 mum. Transmission-electron microscopy investigations indicate that the sub-stoichiometric WO3 nanorods, prepared at about 830 degreesC under the atmosphere of H-2 and Ar mixture, could grow along the either <001> or <110> direction with evident stacking faults and textural structure. Nanorods prepared without H-2 atmosphere are found to be respectively W18O49 grown at around 900 degreesC and WO2.9 grown at 800 degreesC. (C) 2004 Elsevier B.V. All rights reserved.