Supported transition metal catalysts found to be active in the decomposition of acetylene were tested in the production of multiwall carbon nanotubes from methylacetylene. Monometallic (Co or Fe) and bimetallic (Fe,Co or Ni,V) samples were compared using three different types of catalyst support (silicagel, zeolite, alumina). Catalytic activity was characterized by the amount of deposited carbon, selectivity of carbon nanotube formation was estimated by transmission electron microscopy. Except for silica-supported catalysts, all samples were selective in MANT synthesis. (C) 2002 Elsevier Science B.V. All rights reserved.