Recent interests in EOS studies are extended to polymers and associating systems for which various investigators reported considerable successes. Among extensively studied EOS's are following three groups; a cubic EOS with an excess free energy-based mixing rules, hard sphere chain-based theories, and lattice fluid-based models. To evaluate the applicability of these EOSs, a typical EOS was chosen from each group and the results are compared for their accuracies in predicting bubble point pressures, vapor mole fractions, and activities based on the identical data sets of various nature. All three models were found generally less accurate in the critical region and for non-polar polymers in polar but non-associating solvents. Cases in which a model does better or worse were identified and discussed. Also discussed were parameter characteristics and the computation time.