Rapid expansion of a supercritical solution into a liquid solvent (RESOLV) was applied to the nanosizing of ibuprofen particles in aqueous suspension. When the rapid expansion was into neat water, the initially formed nanoscale ibuprofen particles agglomerated into large aggregates. Various water-soluble polymers of different molecular weights were added to the aqueous receiving medium in RESOLV as stabilization agent for the produced nanoparticle suspension, and their effects on the properties of the harvested ibuprofen nanoparticles were evaluated. A conclusion is that the selection of stabilization agent in RESOLV may also be used to alter the sizes and morphology of the nanosized drug particles. (c) 2006 Elsevier B.V. All rights reserved.