In the polymer industry, separation equipment is required to separate unreacted monomers and solvents from polymers. In order to design such equipment, the solubilities of gases and vapors in molten polymers are needed as fundamental data. Activity coefficients at infinite dilution and finite concentrations of solvents in polymer solutions have been measured using gas chromatography. The polymers discussed in this paper are poly(ethylene oxide), poly(vinyl acetate), poly(methyl methacrylate), and poly(vinyl chloride-co-vinyl acetate). The solvents are benzene, toluene, acetone, 2-butanone, n-hexane, ethanol, ethyl acetate, and vinyl acetate. The temperature range is 353-404 K. The experimental data have been compared with those obtained using a cubic-perturbed equation of state with the G(P=0)(E) mixing rule combined with the ASOG group contribution method. The average deviation between the experimental and predicted values is 15%. (c) 2004 Elsevier B.V. All rights reserved.