Highly ordered polycrystalline CdSe nanowire arrays have been synthesized by direct current (dc) electrodeposition in anodic alumina membrane (AAM) from ammonia alkaline solution containing CdCl2 and SeO2. These nanowires have uniform diameters of about 60 nm, which correspond to the pore sizes of the membranes used. The X-ray diffraction (XRD) patterns indicate that the CdSe nanowires crystallize in a wurtzite structure. The X-ray photoelectron energy spectroscopy and the energy dispersing analysis spectroscopy investigations demonstrate that stoichiometric CdSe is formed, and the ratio of selenium to cadmium depends on the pH of the deposition bath. A mechanism for the nanowires growth is suggested.