Co nanowires with a preferred orientation were fabricated by direct current electrodeposition into the pores of porous anodic alumina membrane, and the structure of Co nanowires was Studied by X-ray diffraction and high-resolution transmission electron microscopy with selected-area electron diffraction. It is found that the crystal structure of Co nanowires lies on the deposition potential. When electrodeposition is performed far from equilibrium conditions, i.e., at a high potential, face-centered cubic Co nanowires are deposited, while hexagonal close packing Co nanowires are formed at the low potential. The experimental results indicate that the orientation of the nanowires has effects on the coercivity for both hexagonal close packing (hcp) and face-centered cubic (fcc) Co. (c) 2007 Elsevier B.V. All rights reserved.