Poly(methyl methacrylate) (PMMA) microparticles have been made by dispersion polymerization of methyl methacrylate (MMA) using PDMS-g-pyrrolidone carboxylic acid (Monasil PCA), a CO2-philic stabilizer, in supercritical carbon dioxide. The sizes of the resulting polymer particles were in the range of 2.6-5.0 mum. As the amount of surfactant increased, the particle size became smaller and the size distribution, more uniform. Among the three different amounts of initiator between I and 2% of monomer, 1% gave the best particle size, morphology as well as molar weights of polymer. These PMMA particles were stable in the aqueous buffer solution containing Pluronic L62 surfactant. By sonication the agglomerated polymer particles were disrupted to form small primary particles and the sonicated emulsion was more stable than the original one. (C) 2003 Published by Elsevier B.V.