A simple approach to fabricating tungsten trioxide tubes was developed. Tungsten wires were heated at around 800 degrees C in a humid argon flow and hexagon-shaped tubes with well faceted end and side surfaces resulted. As observed with a scanning electron microscope (SEM), the tubes were about 1 mu m in cross-sectional dimension and 10 mu m in length. The selected-area electron diffraction (SAED) pattern obtained in the transmission electron microscopy (TEM) study revealed that the tubes were hexagonal tungsten trioxide (h-WO3) crystals. The formation of the well-faceted tubular structure is attributed to the lateral coalescence of WO3 nanowires accompanied with a dehydration process. (c) 2006 Elsevier B.V, All rights reserved.