The laser pyrolysis as a tool for the gas-phase synthesis of nanoparticles is illustrated with recent results obtained in the preparation of iron-based nanostructures, where sensitized iron pentacarbonyl-based mixtures and ethylene as energy transfer agent are employed. The relation between the principal process conditions and the product characteristics is stressed. Iron-carbon core-shell nanoparticles with low mean size (about 4-5 nm) and modified morphologies are obtained by an increase of ethylene flow. In case of gamma-iron oxide nanopowder synthesis, low carbon contamination by ethylene depletion at increased system pressure, is observed. (c) 2005 Elsevier B.V. All rights reserved.