We prepared uniform CdS nanowire arrays ways with lengths up to 5 $mu extrm{m}$ and diameters as small as 20 nm by electrochemically depositing the semiconductor directly into the pores of anodic alumina films from an electrolyte containing $CdCl_2$ and S in dimethyl sulfoxide. The nanowire arrays were characterized by scanning electron microscopy and X-ray diffraction. The deposited materials are composed mainly of hexagonal CdS with (100) preferential orientation.