The Peng-Robinson equation of state las modified by Stryjek and Vera), combined with the Wong-Sandler mixing rule, was used for the prediction of excess enthalpies of highly nonideal mixtures at both low and high pressures, and with supercritical components included. In this work, the model parameters were fitted only to experimental vapor-liquid equilibrium data and were then used to obtain simultaneous representation of both vapor-liquid equilibria and excess enthalpy data. The results show that this equation of state model is able to yield not only qualitative, but also reasonably quantitative, predictions of the thermodynamic properties of nonideal systems of varying complexity.