Multiwalled carbon nanotubes (MWCNTs) have been obtained by decomposing molybdenum hexacarbonyl under air or argon in a closed cell, In addition to the carbon nanotubes (CNTs), Mo2C was obtained, A high percentage of CNT was obtained from only a few graphitic carbon particles, Our proposed mechanism suggests that CNT is formed via the Boudard reaction as well as by the reduction of CO by Mo. (C) 2002 Elsevier Science B.V. All rights reserved.