A technique is described for fabricating arrays of uniform CdS nanowires with lengths up to 1 mu m and diameters as small as 9 nm by electrochemically depositing the semiconductor directly into the pores of anodic aluminum oxide films from an electrolyte containing Cd2+ and S in dimethyl sulfoxide. The nanowire arrays were characterized by powder X-ray diffraction (XRD) and electron microscopy. The deposited material is found to be hexagonal CdS with the crystallographic c-axis preferentially oriented along the length of the pore. The effects of annealing on the crystallinity of the deposited semiconductor were investigated by XRD and resonance Raman spectroscopy. The deposition technique is, in principle, generalizable as a means of fabricating nanowires of a wide range of semiconductors.