The catalytic synthesis of carbon nanotubes by pyrolysis of acetylene over Zr based AB(2) and Mm (Misch metal) based AB(5) alloy hydrides is discussed. The alloy-hydrides have been prepared using hydrogen decrepitation technique. The samples were purified by acid and heat treatment and were characterized by XRD, BET surface area measurements, SEM, TEM and Raman spectroscopy. A maximum adsorption capacity of 3.3 and 3.1 wt% are obtained at 298 K and 100 bar for carbon nanotubes prepared with Mm based AB(5) and Zr based AB(2) hydrogen storage alloy hydride catalysts, respectively. (C) 2003 Elsevier Science B.V. All rights reserved.