Carbon nanotubes (CNTs) were synthesized using chemical vapor deposition of ferrocene and acetylene in the temperature range 600-800 degreesC. The growth rate increases exponentially with the temperature, providing an activation energy 30 kcal/mol which is close to the diffusion energy of carbons in the bulk iron metal. We compared the growth rate with those of the CNTs. gown using other thermal methods reported previously and suggest a simple kinetic model to explain the growth rate depending on the method. The supply rate of C atoms in gas phase would influence the growth rate of CNTs. (C) 2004 Elsevier B.V. All rights reserved.