Ultra-fine ZnO nanowires can be easily synthesized at 800degreesC in air via oxidation of Zn nanowires which is produced by heating ZnO + C mixture at 1100degreesC under a flow of nitrogen gas. Field-emission scanning electron microscope and transmission electron microscope investigations show that the ultra-fine ZnO nanowires grown out from Zn nanowires are high-quality single nanocrystals. The diameter of the ultra-fine ZnO nanowires ranges from 8 to 20 nm and their length is 400 nm-1 mum, having a high aspect ratio of similar to50. The growth mechanism of the ultra-fine ZnO nanowires is discussed. (C) 2004 Elsevier B.V. All rights reserved.