A method to grow multi-wall carbon nanotube bundles in a high yield (weighing over 15 times the catalyst) is developed and a plausible explanation for the formation and high yield of the bundles is suggested. The Co-Mo-Mg-O catalyst used in the experiment is prepared by a sol-gel technique, molybdenum being doped into the catalyst through oxidation and diffusion at 750 degreesC. Small changes to the catalyst preparation lead to the growth of single-wall carbon nanotubes (SWIM). Our work is an exploitation of the high performance of the solid catalyst in the synthesis of novel nanomaterials. (C) 2002 Elsevier Science B.V. All rights reserved.