A method is proposed to predict vapor-liquid equilibria (VLE) of aqueous mixtures by using the NRTL equation The algorithm closely follows that reported in previous works dealing with predictions of VLE of non-aqueous mixtures. The main assumptions are : simple rules can be derived for families of mixtures characterized by similar chemico-physical properties; within each family, the energy interaction parameters of the NRTL equation can be calculated by knowing only the well-known properties of the pure compounds, such as the Hildebrand solubility parameters. The main subdivision adopted in this work is between soluble mixtures and mixtures with a solubility gap. Soluble mixtures are subdivided, in turn, into four sub-classes : H2O/C1-C4 alcohols, H2O/amines; H2O/heterocyclic compounds or amides : H2O/other polar compounds. The method is applied to several binary mixtures which represent difficult cases, as strongly associated or highly asymmetric systems. For some systems a comparison is made with the group contribution method. New relationships which improve the prediction of VLE of non-aqueous systems are also reported.