Catalytic decomposition of methane is a potential alternative route for the production of hydrogen from natural gas. In the present paper we report the results of hydrogen production in the TCD of methane over Ni-Mg and Ni-Cu-Mg catalysts prepared by co-precipitation, impregnation and fusion methods. The characterization of the catalysts used and the carbon obtained is also presented. Whatever to be the preparation method, all the catalysts show a high and almost constant methane decomposition rate without deactivation after 8 h on stream. The presence of copper enhances hydrogen production and the best results were obtained for Ni-Cu-Mg catalysts prepared by the fusion method, reaching a hydrogen production of 80 vol.%. For the Ni-Mg catalysts, the nickel crystal size influences on the catalysts performance so that the highest the crystallite size the lowest the hydrogen yields. In contrast, for the Ni-Cu-Mg catalyst the Ni particle size has not a significant influence on the hydrogen yields. All catalysts tested promote formation of filamentous carbon some micrometers long and with a fiber diameter highly dependent on the presence of Cu: Ni-Mg catalysts promote the formation of fibers with homogeneous diameter around 30 nm while Ni-Cu-Mg catalysts lead to the formation of fibers of inhomogeneous and bigger diameter. (C) 2007 Elsevier B.V. All rights reserved.