The group-contribution, lattice-fluid (GCLF) equation of state (EoS) is now more than 10 years old. The primary objective of our effort has been to develop a predictive model for the phase equilibria in polymer-solvent systems. The model has been developed by introducing group-contribution to the Panayiotou-Vera EoS. This paper reviews and updates the application of this approach along with its shortcomings. This EoS has been applied to prediction of the density of pure polymers, VLE of vapors, supercritical gas solubility, LLE, solubility parameters, and glass transition temperatures. Homopolymers and random copolymers can be successfully treated. The key features of this model are that it is purely predictive based only on the molecular structure of the molecules, and it is able to describe the pressure as well as temperature and composition effects because it is based on an EoS.