The micronization of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) from organic solutions using supercritical antisolvent (SAS) technique has been successfully achieved. SAS experiments were carried out at different operational conditions and microspheres with mean diameters ranging from 3 to 9 mu m were obtained. The effect of CO2 and liquid flow, temperature and pressure on particle size and particle size distribution was evaluated. The microspheres were precipitated from a dichloromethane (DCM) solution. The best process conditions for this mixture were, according to our study, 40 degrees C, 100 bar, 1 mL min(-1) liquid flow and 10 L min(-1) carbon dioxide flow. Experiments with polymers containing different HV percentages were carried out. The powders obtained became more spherical as the HV content decreased. (c) 2006 Elsevier B.V. All rights reserved.