AbstractCOSMO‐RS, a general and fast methodology for the a priori prediction of thermophysical data of liquids is presented. It is based on cheap unimolecular quantum chemical calculations, which, combined with exact statistical thermodynamics, provide the information necessary for the evaluation of molecular interactions in liquids. COSMO‐RS is an alternative to structure interpolating group contribution methods. The method is independent of experimental data and generally applicable. A methodological comparison with group contribution methods is given. The applicability of the COSMO‐RS method to the goal of solvent screening is demonstrated at various examples of vapor–liquid‐, liquid–liquid‐, solid–liquid‐equilibria and vapor‐pressure predictions.