We report on the synthesis and elemental mapping of ropes composed of aligned multi-walled B-C-N nanotubes using energy-filtered (Omega filter) high-resolution transmission electron microscopy. The nanotube ropes were synthesized by reacting aligned CNx (x less than or equal to 0.1) nanotubes with B2O3 in a N-2 atmosphere at 1985-2113 K. It was found that the overall B-N content within the ropes increases with temperature. Furthermore, BN-rich tubular ropes obtained at higher synthesis temperatures exhibit complex shell assembly: BN-rich, C-rich and B-C-N layers were found to exist. The latter nanostructure represents a unique 'nanocable' with either conducting or semiconducting shells shielded with insulating BN-rich layers. We envisage that the novel nanocables will also exhibit high-oxidation resistance at elevated temperatures. (C) 2002 Elsevier Science B.V. All rights reserved.