This work has as main objective the development of a model process to obtain microparticles of an acrylate-methacrylate copolymer (Eudragit L100(R) and Eudragit EPO(R)) using supercritical carbon dioxide (SC-CO2) as antisolvent (GAS). After studying the behaviour of the copolymers in SC-CO2 at different operation conditions (pressure, temperature and presence of ethanol (EtOH)), efforts were invested in the optimization of Eudragit EPO(R) precipitation from an organic solution using carbon dioxide as antisolvent in batch mode. After loading the precipitation vessel with a fixed quantity of the copolymer dissolution, the SC-CO2 has been added until the pressure of operation has been reached. Three process parameters, namely, solution nature, presence of surfactants and organic solvent removal step, have been evaluated. Microparticles with mean diameter from about 2 to 12 mu m are obtained. (C) 2009 Elsevier B.V. All rights reserved.