We report a new strategy for the production via supercritical fluid extraction of emulsion of biocompatible magnetic nanocomposite particles made of magnetite nanocrystals dispersed in a poly(lactic-co-glycolic) acid (PLGA) matrix. Ricinoleic acid-stabilized magnetic nanocrystals have been prepared via coprecipitation of two iron salts in alkaline environment, and subsequently dispersed in a solution of PLGA in dichloromethane. The obtained oil phase has then been dispersed in an aqueous solution of polyvinyl alcohol (PVA) in order to obtain a kinetically stable oil-in-water miniemulsion. The solvent was finally extracted via supercritical fluid extraction of emulsions. The continuous extraction of dichloromethane by means of supercritical CO2 leads directly to a stable suspension of magnetite PLGA composite nanoparticles in water. The influence of those parameters affecting the final particle size distribution and morphology, primarily emulsifier amount and magnetite content, has been investigated, so as to optimize the process. Analysis of the products, performed through light scattering and electron microscopy, indicates that narrower size distributions are obtained with larger amounts of emulsifier and lower amounts of magnetite. The morphology of the particles tends to be of Janus type, with the magnetite accumulated on one hemisphere of the particle. The proposed approach is suitable for the preparation of large quantities of high-quality magnetite PLGA composite nanoparticles for biomedical applications. (C) 2010 Elsevier B.V. All rights reserved.