Co-Pt-based tubular nanostructures were prepared by direct plating into track-etched polycarbonate templates from a single electrolyte containing a Pt-p-salt and Co-sulphamate. These tubular nanostructures. with a diameter of 200 nm and lengths up to 5 mu m, were obtained with potentiostatic depositions at potentials of -1.9 V to -2.5V, measured against a Ag/AgCl electrode for 60 min A detailed TEM/EDS analysis showed that the tubes consisted of randomly orientated nanocrystals of an FCC Co-Pt phase and that the composition of an individual nanotube varies along its length. The formation mechanism of the Co-Pt-based tubular nanostructures can therefore be explained via partial Au-coverage of the template and the appropriate relative rates of the deposition and diffusion of the Pt and Co electro-active species, most probably assisted by hydrogen evolution The as-deposited Co-Pt-based nanotubes, with an aspect ratio of 10, are magnetically isotropic and have a coercivity of 10 kA m(-1). The easy axis of the magnetization was found to be perpendicular to the axis of the tube (c) 2009 Elsevier B.V. All rights reserved.