Bulk-quantity GaN nanowires of wurtzite hexagonal structure were synthesized by using hot-filament chemical vapor deposition. GaN nanowires showed two distinctive temperature-dependent growth directions. At a substrate temperature of 900-950 degreesC, the growth direction of GaN nanowires was perpendicular to the {1011} plane, while at 800-900 degreesC, the growth direction was perpendicular to 10 0 0 21 plane. The two directions are different from the (10 10) direction, which is common for GaN nanowires grown to date. The difference in growth direction may be due to different growth mechanisms. In this study, the nanowires grew via a vapor-solid mechanism instead of the VLS growth mechanism. (C) 2002 Elsevier Science B.V. All rights reserved.