A model (AGAPE), based on consideration of the properties of whole, rather than segments of molecules, that allows the prediction of phase equilibria in terms of two general physical parameters is presented. One of the parameters is a geometric (or entropic) parameter while the other is an energetic parameter (a net unlike molecular pair interaction energy). Two procedures are presented for estimating these parameters. The first employs ab initio calculations based on the generalised London potential theory which needs only pure component molecular and atomic parameters; the second uses a single experimental vapour-liquid equilibria (VLE) data point. The range of each procedure is explored together with the results of the application of the model (a multicomponent version of which is presented) to the prediction and correlation of VLE and enthalpy data for several binary mixtures. Satisfactory results were obtained.