Vapor-liquid equilibria for the quaternary vinyl acetate – latex system were obtained using the headspace method at 40°C. The Flory - Huggins interaction parameters for the different species in the emulsion polymerization of PVAC latexes are reported. The UNIFAC – FV model by Oishi and Prausnitz was applied to predict vapor-liquid equilibria in the binary and ternary systems containing vinyl acetate, 4-nonyl phenol polyethoxilate surfactant with nine ethoxilate units, and PVAc. The predicted results compare favorably with the experimental data for all systems.