High-quality indium oxide (In2O3) nanobelts were successfully synthesized without catalyst at low temperature ranged from 600 to 850 degreesC using a simple physical vapor deposition. To synthesize the In2O3 nanobelts, we employed a simple reaction of thermally evaporated indium vapor in a wet oxidizing environment. The In2O3 nanobelts have diameters in the range of 20-200 nm and lengths over several hundreds micrometer. The synthesized nanobelts indicate high-purity and single-crystalline cubic structure. Most of In2O3 nanobelts have (100) growth direction but some nanobelts have (110) growth direction. Photoluminescence spectra under excitation at 325 nm showed a strong and broad emission at 570 nm with a shoulder at 630 nm related to oxygen vacancies. We suggest that the synthesis of the In2O3 nanobelts follows the self-assisted growth mechanism in our method. (C) 2003 Published by Elsevier B.V.