We have synthesized the large-scaled gallium oxide nanowire arrays using a reaction of a trimethylgallium (TMGa) and oxygen (O-2) mixture. Scanning electron microscopy revealed that the cross-section of the nanowires had a circular shape with the diameter of about 50-150 nm and the length up to several tens of micrometers. High-resolution transmission electron microscopy showed that the gallium oxide nanowires were of amorphous or polycrystalline nature. (C) 2004 Elsevier B.V. All rights reserved.