Pyrolytic decomposition of acetylene on the surface of nickel-, cobalt-, and iron-containing ordered mesoporous MCM-41 silicas has been studied. Catalytically active matrices have been prepared by chemisorption of volatile metal acetylacetonate complexes on the silica surface. Acetylene is used not only as a source of carbon in synthesis of the nanostructures but also as a reagent reducing metal ions in the surface chemical compounds. Formation of carbon nanotubes and nanowires is shown to depend on the pyrolysis conditions. (c) 2005 Elsevier B.V. All rights reserved.