An extended Flory-Rehner and Regular Solution Theory model framework has been developed for interpreting the swelling behavior of kerogen toward solvents. Thermodynamic parameters controlling the swelling response of kerogen are the solubility parameter, the cross-link density, and the volume fraction of the kerogen network v(eq) that minimizes its elastic strain energy, termed "native swelling". These parameters are obtained by optimizing the match between theoretical predictions and experimental swelling data of kerogen for neat solvents. A good match between theory and experiment is obtained for Draupne Type II kerogen. These results imply that this kerogen behaves like a cross-linked elastomer network and that the interaction with the solvents used involves nonspecific interactions. This model framework enables prediction of the kerogen's response to solvent mixtures. This is an important step toward modeling hydrocarbon expulsion from kerogen during petroleum generation. If the composition of the mixture is made to resemble the primary products of kerogen maturation, it should be possible to predict the equilibrium composition of molecules retained in kerogen with those in the proximate fluid.