Sorption and diffusion of supercritical carbon dioxide (SCCO2) into polysulfone (PSF) from 313 K and 20 MPa to 333 K and 40 MPa were investigated in this study. A simple gravimetric method was used to measure the mass gain of SCCO2 in PSF, and the Fick's diffusion model was applied to describe the desorption process. The sorption amount, the sorption diffusivity under supercritical states, and the desorption diffusivity at ambient conditions are presented. Comparisons of the sorption amounts and diffusivities of CO2 for polymers of polycarbonate and PSF are discussed according to the interactions between gas and polymers. The morphology change and plasticization effect attributed to gas sorption in PSF were studied. Effects of glass-transition temperature and yielding stress for PSF and other polymers were used to describe the difference in their diffusivities for the sorption and desorption processes. (C) 2004 Wiley Periodicals, Inc.