Vapour-liquid equilibria and excess molar enthalpies of binary solutions of acetic acid with water, 2-butanone, methyl acetate and ethyl acetate are calculated using the UNIQUAC associated-solution model, which takes into account the autodimerization of acetic acid and the heteroassociation of unlike molecules. Prediction of ternary liquid-liquid equilibria for the acetic acid + water + nonassociating component systems are demonstrated from the same model with only binary parameters. The calculated results agree well with the experimental values.