Abstract: This paper develops an equation of state method to predict vapor-liquid equilibria (VLE)of mixtures using only pure component parameters. Based on the mixing rule combined with excess Gibbs free energy gE, a model of infinite dilution activity coefficients MOSCED is used to predict the interaction parameters of the activity coefficients equation which calculates the gE. This makes the cubic equation of state into a predictive one for the VLE calculations over a wide temperature and pressure range. Like the UNIFAC group-contribution equation of state, it performs satisfactorily in the VLE prediction of systems containing polar components , including VLE under high pressures.