The catalyst effect on the synthesis of carbon nanotubes (CNTs) using thermal chemical vapor deposition (CVD) was investigated. The respective growth rate of CNTs shows that the performance of catalysts is in the order of nickel (Ni) > cobalt (Co) > iron (Fe). The average diameter of CNTs follows the sequence of, Fe, Co, and Ni catalysts. The structure of CNTs reveals almost same morphology regardless of catalyst but the crystallinity of CNTs is largely dependent on catalyst. The crystallinity of CNTs synthesized from Fe catalyst is higher than that from Ni or Co catalyst, The results indicate that the growth rate, the diameter, and the crystallinity can be manipulated by the selection of the catalyst. (C) 2002 Elsevier Science B.V. All rights reserved.