Sorption of inert gases (He, Ne, Ar, Kr, and Xe) in two rubbery polymers, 1,2-polybutadiene (PB) and poly(ethylene-co-vinyl acetate) (EVAc), and dilation of the polymers due to the sorption were measured as a function of the gas pressure at 25-degrees-C. For all the gases, the sorption isotherms followed the Henry’s law over the pressure ranges examined, and the dilation isotherms were linear in these ranges. From the sorption and dilation data, the partial molar volumes V(R)BAR of the dissolved gases were determined. A linear relation was found between V(R)BAR and the van der Waals volume V(W)BAR; i.e., V(R)BAR = 1.6 V(W)BAR + 20 in cm3/mol. This is much the same as the relation for hydrocarbon gases dissolved in the same polymers and that between molar volume and V(W)BAR for liquid n-alkanes. There also existed a linear relation between V(R)BAR and the logarithm of Henry’s law coefficient for a series of inert gases in the polymers. Sorption and dilation for He/Kr mixtures in PB were measured at various total and partial pressures, and thereby the hydrostatic-pressure dependence of V(R)BAR for dissolved Kr component was examined. From the dependence, the compressibility of the dissolved Kr molecules was estimated to be approximately 5 X 10(-4) atm-1.