This paper describes the initial stages of electrochemical growth of Cu and Ni nanowires in polycarbonate (PC) track-etched membranes as the template. The diameters of the wires ranged from 50 to 200 nm. A thin Pt-Pd layer (similar to 30nm thick) was sputter-deposited onto one side of the membrane and used as the cathode. The layer was not thick enough to seal the pore mouths. Cathodic current in the early stages of both Cu and Ni electrodeposition abruptly decreased after a period proportional to the pore diameter. Growing Cu grains plugged the pore openings causing the current to decrease, while the Ni deposition initially yielded a hollow tube in each pore resulting in a nanostructure transition of the tube to the wire at the growth front and a decrease in the current. (C) 2007 Elsevier Ltd. All rights reserved.