The preparation of multi-walled carbon nanotubes (MWCNTs) by chemical vapor deposition (CVD) method using nanocrystalline CaCO3 as metal catalyst support was investigated, where acetylene was used as carbon source, and Co, Fe and Ni, as well as their bimetallic compounds as the active component of the catalyst. The smaller size of the CaCO3 support led to a much higher yield of CNTs than previously reported. It was noteworthy that the best performance was Fe-Co nanoparticles, which gave a high yield of CNTs, as judged by experimental results. Growth temperature affected catalytic activity and the disintegration of the support. The raw product was purified to a high level, with little damage on the CNT structure, as confirmed by thermal gravimetric (TG), micro-Raman and transmission electron microscopy (TEM) analyses. (c) 2005 Elsevier B.V. All rights reserved.