The interest in the preparation and application of nanometer size materials is increasing since they can exhibit properties of great industrial interest. Several techniques have been proposed to produce nanomaterials using supercritical fluids. These processes, taking advantage of the specific properties of supercritical fluids, are generally flexible, more simplified and with a reduced enviromental impact. The result is that nanomaterials with potentially better performances have been obtained. We propose a critical review of the supercritical based techniques applied to the production of nanoparticles, nanofibers, nanowires, nanotubes, nanofilms and nanostructured materials. The most relevant characteristics of each process and the kind of nanomaterial that can be produced are highlighted. (C) 2005 Elsevier B.V. All rights reserved.