Large-scale GaN nanowires (GNWs) were prepared by thermal evaporation of conventional GaN powders (CGPs) under controlled conditions without involvement of any template or patterned catalyst. The as-synthesized GNWs are about 30 nm in diameter and several hundreds of microns in length. The growth of GNWs is controlled by the conventional vapor-solid mechanism. Dielectric properties of GNWs and CGPs are measured in the frequency range of 10(2)-10(7) Hz. The data obtained indicate that the grain size of samples has great influence on the dielectric properties, where the corresponding mechanism is discussed. (C) 2003 Elsevier Science B.V. All rights reserved.