In this paper, we discuss the sorption thermodynamics of gases in polymeric solvents with particular emphasis on the contributions of solute binding and solvent reorganization to the partial heat of gas sorption. Molecular interpretation of these contributions provides useful insights in molecular mechanisms of gas sorption and explanations of endo- and exo-thermic heat effects, which may both occur depending on the nature of the gas molecule and the (polymeric) solvent. Molecular dynamics simulations have been performed to calculate several solvation quantities for a series of gas penetrants in liquid dodecane and liquid (rubbery) poly(ethylene), as well as for glassy poly(vinyl chloride) and poly(vinyl alcohol). The differences in solvation behavior of the liquid solvents are discussed in detail and it is shown that, at the glass transition temperature of the glassy polymeric solvents, the Van't Hoff representation of temperature dependent sorption data may pass through a minimum,