A novel and very efficient method for the a priori prediction of thermophysical data of liquids is presented. It is based on unimolecular quantum chemical calculations that provide the necessary information for the evaluation of molecular interactions in liquids. Combined with a very fast and accurate statistical thermodynamics, the new method is an alternative to structure-interpolating group contribution methods (GCMs), The most important advantages are the essentially general applicability, the sound physical basis, and the graphicness of the procedure, which easily allows for chemical interpretation and understanding of thermophysical behaviour. A methodological comparison with GCMs is given. Example applications are presented.