Four catalysts, consisting of Ni, Ni:Cu, Fe or Fe:Mo as the active phase and Al2O3 or MgO as a textural promoter, were tested for the catalytic decomposition of methane in a rotary bed reactor, obtaining both CO2-free hydrogen and carbon nanostructures in a single step. Hydrogen yields of up to 14.4 Ndm(3) H-2.(h.g(cat))(-1) were obtained using the Ni-based catalysts, and methane conversions above 80% were observed with the Fe-based catalysts. In addition to hydrogen production, the Ni-based catalysts allowed the large-scale production of fishbone-like carbon nanofibres, whereas the use of the Fe-based catalysts promoted the production of carbonaceous filaments having a high degree of structural order, consisting of both chain-like carbon nanofibres and carbon nanotubes. (C) 2011 Elsevier B.V. All rights reserved.