Four equations of state, two cubic and two perturbed hard-sphere equations, are examined with regard to their prediction of vapor-liquid equilibria. The computed predictions are compared with experimental data. Results of the comparison are reported for mixtures of polar, non-polar, and highly associated compounds. The experimental data base of the comparison includes fifteen binary systems covering a wide range of pressure, temperature, and molecular variety. The same computational technique was used throughout this study. The results indicate that both cubic equations give better predictions of the vapor-liquid equilibria for non-polar and symmetric mixtures, while both perturbed hard-sphere equations give significantly better predictions for the highly asymmetric and associated systems of CO2-fatty acid methyl esters. All equations failed to predict the vapor-liquid, equilibria for, some mixtures, especially the highly associated systems. However, the phase equilibrium behavior of these systems is greatly improved using mixing rules other than the simple quadratic mixing rule. Generally, no single equation of state currently exists that is equally suitable-for the prediction of vapor-liquid equilibria of all classes of binary systems.