This work presents the results concerning the preparation of polymeric membranes from polyethersulfone (PES), and characterization of their behavior in dense CO2 medium at 23 and 40degreesC. The membranes were prepared by coagulation of polymeric solutions at 35 wt.% in a nonsolvent bath, and the effect of temperature of the coagulation bath on membrane characteristics was studied. Each membrane was characterized in terms of permeability to dense CO2 and retention of poly(ethylene glycol) of average molecular weight 1000 g/mol (PEG 1000). The decrease in the coagulation water bath temperature from 40 to 5 degreesC resulted in denser membranes, able to retain up to 90% of PEG 1000, but also with smaller permeability to dense carbon dioxide.