A simple electrochemical method is described for producing metal or semiconductor nanowires with diameters in the continuous range 10 to 200 nm. The technique involves a three-step process that begins with the electrochemical generation of an aluminum oxide template with uniform nanometer-sized pores, followed by the deposition of metal or semiconductor in them. The nanowires are then exposed for study or device fabrication by etching back the oxide matrix. Examples of cadmium nanowires fabricated by this technique are shown.