The Ni nanowires with different diameters were prepared by direct-current electrodeposition into the pores of porous anodic alumina membrane. The growth orientation of Ni nanowires with different diameters can be along [110] or [111] direction by adjusting the electrodeposition conditions. The micrographs and crystal structures of nanowires are studied by field-emission scanning electron microscopy, high-resolution transmission electron microscopy, and X-ray diffraction. The change of the growth orientation is analyzed in light of thermodynamics and electrochemistry. It is expected that the ability to control the growth orientation of nanowires could open up new opportunities for fundamental studies and the application of nanostructures. (c) 2007 The Electrochemical Society.