Carbon submicrotubes were synthesized on carbon microfibers by floating catalyst method, and carbon nanotubes were also observed to grow on the rough surface of carbon submicrotubes. The morphology, microstructure and composition of the obtained products were characterized by field emission scanning electron microscopy, high-resolution transmission electron microscopy, Raman spectroscopy and energy dispersive X-ray spectroscopy. The growth of carbon submicrotubes on carbon microfibers; was attributed to the pretreatment of carbon microfibers, which gave rise to catalyst areas, while the secondary growth of carbon nanotubes could be related to the defects of hexagonal graphite on the surface of carbon submicrotubes. (c) 2008 Elsevier B.V. All rights reserved.