This work reports sorption processes of oxygen, carbon dioxide, methane, ethylene, and propylene in films of both vulcanized natural rubber and vulcanized rubber-regenerated cellulose composites. The curves representing the pressure dependence of the concentration of carbon dioxide in the composites clearly exhibit a slight concavity with respect to the abscissa axis as a result of adsorption processes taking place in Langmuir sites located in the glassy cellulose component. Adsorption processes are also detected in the sorption curves of ethylene at low pressures. The concavity with respect to the ordinate axis of the curve concentration of propylene versus pressure at high pressure is pretty well described by the Flory-Huggins formalism. The solubilities of the other gases mainly obey Henry's behavior, adsorption processes in the glassy component being in most cases negligible. Values of the interaction chi parameter for gas-natural rubber and gas-natural rubber composites are obtained from the comparison of the experimental solubility coefficients with those predicted by the Flory-Huggins theory. The theory suggests that Henry's constant is a linear function of the boiling temperature of the gases. (c) 2005 Wiley Periodicals, Inc.