Thiophene was introduced as an additive in detonation-assisted chemical vapor deposition to investigate the effect of sulfur on the growth of carbon nanotubes. The results reveal that sulfur promoted the growth of hollow tubes, instead of bamboo-like carbon nanotubes without sulfur addition. Structural characterization of products indicates that the dynamic reshaping of the catalyst assisted bamboo-like carbon nanotube growth and the bamboo knots preferentially nucleated on the Ni-graphite step edges. It is suggested that sulfur suppressed the bamboo knot growth through blocking the step sites. The findings are important for understanding of nanotube growth mechanism and the role of sulfur often involved in catalytic reactions. (C) 2010 Elsevier B.V. All rights reserved.