Electrodeposition was used to fabricate metallic CoNiCu and Cu nanotubes in polycarbonate membranes. The tubes were obtained from a low-efficiency CoNiCu electrolyte, critical to the evolution of tube formation. Tube wall thickness was assessed and alloy tubes filled with Cu metal demonstrated. A high-efficiency electrolyte was used to show the importance of the side reaction on the nanotube formation. Nanowires were obtained in the high-efficiency electrolyte while nanotubes were generated from the low-efficiency electrolyte. Both gas evolution, resulting from electrodeposition, and partial pore coverage on the bottom of the membranes accounted for the tube formation. (C) 2004 The Electrochemical Society.