The enthalpy of mixing at 341.45 K of an ethylene-vinyl acetate copolymer mixed with a docosanyl diester of poly(ethylene glycol) has been determined as a function of composition by mixing calorimetry. Endothermic enthalpies were obtained with values in the range 2 to 15Jmol(-1) Small-angle neutron scattering has been used on similar mixtures where the diester was perdeuterated to obtain the effective interaction parameter over the temperature range 353 to 383 K for a volume fraction of ethylene-vinyl acetate copolymer in the mixture from 0.81 to 0.27. The temperature dependence of this effective interaction parameter has been used to obtain the enthalpic contribution. This latter parameter was compared with that obtained from the enthalpy of mixing. Although exact agreement is not obtained, the values are reasonably close and the differences can be attributed to the effect of deuterium labelling on the interaction between the constituents of the polymer blend.