Coprecipitated Fe-Al2O3, Fe-Co-Al2O3 and Fe-Ni-Al2O3 catalysts is shown to be very efficient in carbon deposition during methane decomposition at moderate temperatures (600-650 degreesC). The carbon capacity of the most efficient bimetallic catalysts containing 50-65 wt.% Fe, 5-10 wt.% Co (or Ni) and 25-40 wt.% Al2O3 is found to reach 145 g/g(cat), Most likely, their high efficiency is due to specific crystal structures of the metal particles and formation of optimum particle size distribution. According to the TEM data, catalytic filamentous carbon (CFC) is formed on them as multiwall carbon nanotubes (MWNTs). The phase composition of the catalysts during methane decomposition is studied using a complex of physicochemical methods (XRD, REDD, Mossbauer spectroscopy and EXAFS). Possible mechanisms of the catalyst deactivation are discussed. (C) 2004 Elsevier B.V. All rights reserved.