This work illustrates the use of high pressure gases to influence the solubility and diffusion behavior of solvents in polymers. High pressure inverse gas chromatography was used to measure partition and diffusion coefficients of solvents in poly(styrene) and poly(vinyl acetate) using CO2 and ethylene as high pressure carrier gases. A comparison of the two gases is made in terms of their effect on the systems. In addition, influences due to solvent size were examined. The results of this work could lead to significant improvements in polymer devolatilization processes.