Uniform tungsten oxide nanowires with small diameter have been fabricated with potassium hydroxide as catalyst on a tungsten plate and by the method of thermal evaporation via a unique two-step heating process. Typical temperatures of this two-step process are 390 and 610 degrees C, respectively. The first-step heating was found crucial for the growth of small and uniform nanowires because it made the potassium hydroxide solution more uniformly distributed on the tungsten plate surface. The structure and composition of the grown nanowires were characterized by various methods. The diameter of the nanowires ranges from 30-200 nm and the length is up to several tens of micrometers. The structure of the nanowires is found to be orthorhombic tungsten oxide (W3O8), with cell parameters a = 1.035 nm, b = 1.399 nm, c = 0.378 nm. (c) 2007 Elsevier B.V. All rights reserved.