Porous structures of pOly(L-lactic acid) (PLLA) were prepared using supercritical CO2 as antisolvent. The uniform cross-sections and the cellular pores of the final samples indicated the occurrence of a liquid-liquid (L-L) demixing process, followed by crystallization of the polymer-rich phase, as the dominant mechanism of the phase separation and pore production. The effect of pressure, temperature and initial concentration of the polymer solution on the final porous structure were investigated. The average pore size decreased with the increase of CO2 density either by increasing the pressure or by decreasing the temperature, while the average pore diameter decreased with the increase of the initial polymer concentration. (C) 2006 Elsevier B.V. All rights reserved.