Ensembles of graphite-based nanotubes (see Fig.) have been produced by extending a template approach successfully used for metals and semiconductors to carbons. The outer and inner diameters of the tubules can be controlled by varying the time allowed for the polymerization of acrylonitrile within the pores of a nanoporous membrane, The polyacrylonitrile nanotubes formed in the pores are subsequently graphitized at high temperatures to form the graphitized nanotubes.