An analysis of EoS/GE models, which are based on matching the EoS-derived expression for the excess Gibbs free energy GE with that from a GE model at zero pressure, is presented, with the focus on the most successful and widely used of these models, MHV2 and PSRK. It shows why zero-reference-pressure models do not reproduce exactly the GE models at zero pressure and the ensuing implications on the prediction of asymmetric systems. The development of EoS/GE models that reproduce exactly the GE model is discussed. However, such reproducibility at zero pressure is impossible for systems containing components with reduced temperatures higher than about 0.9. Therefore, extrapolation schemes that allow treatment of such systems are examined.