In this process carbon nanotubes were prepared by the pyrolysis of a gaseous hydrocarbon in contacting with Ni nanowires, which were typically a few microns long, electrochemically produced from an anodic aluminium oxide template. Under controlled conditions, carbon nanotubes were formed at the location of the Ni-nanowire template. They inherited the shapes of the Ni nanowires, with their inner diameter being same as the outer diameter of the Ni nanowires. A novel growth mechanism which involves the diffusion of Ni atoms and the reshape of Ni nanowires is discussed. (C) 2004 Elsevier B.V. All rights reserved.