The Perturbed Soft Chain Theory (PSCT) has been evaluated extensively for application to vapor-liquid equilibrium calculations in polymer-solvent systems. Pure compound parameters for many common solvents and polymers have been determined by using experimental data from two major data bases. Predictive and correlative capabilities of the PSCT have been compared for non-polar, non-polar/polar, and polar/polar systems over the entire concentration range. The model can represent the mixture experimental data behavior when a small binary interaction parameter is introduced to correct for energetic interactions. An extensive data base of binary interactions parameters for more than 50 polymer-solvent systems has been generated. The effects on the mixture calculations of uncertainties in determining the pure compound parameters have also been analyzed.