The growth behavior of ZnO nanowires on an anisotropic crystalline substrate has been investigated in this work. On both the vicinal Si(1 0 0) substrate with a 6degrees miscut angle in the [0 (1) over bar(1) over bar] Si direction and the on-axis Si(1 0 0) substrate, ZnO nanowires have been directly grown by thermal evaporation using the ball-milled ZnO powders under controlled conditions without the presence of catalyst. In this work, we confirmed that the vicinal surface of the substrate leads to selective growth during the initial growth of ZnO nanowires. For the vicinal substrate that consists of terraces separated by steps, ZnO nanowires are preferentially grown near step-edge lines aligned along the [0 1 (1) over bar ] Si azimuth. For the on-axis substrate, on the other hand, ZnO nanowires are randomly grown on the whole surface of the substrate. In addition, the average diameter of the nanowires grown on the vicinal substrate is slightly thinner than that of the nanowires grown on the on-axis substrate. The vapor-solid model is also proposed to explain the growth behavior of ZnO nanowires in our synthesis process. (C) 2002 Elsevier Science B.V. All rights reserved.