ZnO nanowires array has been synthesized via a simple physical vapor deposition method at low growth temperature without using any catalyst. By controlling different growth parameters, the nanowires exhibit different shapes: needle-like with sharp tips or rod-like with flat tips. All the nanowires are single crystal with a growth direction along c-axis. The rod-like nanowires are well vertical aligned to the substrate surface with c-axis preferred orientation. The morphology difference of ZnO nanowires is believed originated from different growth mechanisms. © 2005 Elsevier B.V. All rights reserved.