Carbon nanotubes (CNTs) production is investigated by the combination of catalyst reduction and methane decomposition over a nickel and a cobalt catalyst in a fluidized bed reactor, respectively. Higher conversion of methane is observed in the combined process of the catalyst reduction and methane decomposition, and the yield of CNTs in the combined process is about 3-4 times that in the separated methane decomposition process. The effect is probably attributed to the lattice oxygen on the unreduced catalyst, in presence of which the simultaneous catalyst reduction provides energy for the endothermic methane decomposition and consumes part of hydrogen and carbon (to the H2O and CO), making the equilibrium of methane decomposition shift to the direction of hydrogen and CNTs production in a much higher reaction rate. (C) 2003 Elsevier B.V. All rights reserved.