A new equation of state (EOS) was formulated by the nonrandom two-fluid approximation of the lattice-hole theory. The resulting EOS contains two molecular parameters for a pure fluid and one additional interaction parameter per binary. The model was tested for its applicability over a wide range of density and pressure to purl properties of supercritical fluids and high pressure phase equilibria of mixed systems containing molecules of arbitrary size and shape. Results obtained to date demonstrate that the new EOS correlates quantitatively well the various types of experimental supercritical and multiphase equilibria. To our knowledge, no other molecular theory originated from the classical lattice fluid description has been presented which describes an entire range of densities of pure fluids and mixtures from a unified point of view.