Novel correlations are proposed for the solubility coefficients of gases (S) as well as the parameters of the dual mode sorption isotherms k(D) and b in polymers. They are based on the concept of molecular surface areas of dissolved species. Van der Waals surface areas (WSA) as estimated using UNIFAC group contributions and solvent accessible surface areas (SASA) were considered as possible parameters for correlations. Excellent dependencies with correlation coefficients R in the range 0.95-0.99 were obtained for the correlations of ln S, ln k(D), and ln b with surface area. (C) 2000 John Wiley & Sons, Inc.