Abstract A new predictive method for estimation of accurate thermodynamic properties of the liquid-vapor coexistence states is presented. The new method is based on the predictive methods by Pitzer, Lee and Kesler, and Armstrong and Teja. Calculated values of vapor pressure and saturated liquid density for argon, nitrogen, ethylene, oxygen, fluorine, methane, dichlorodifluoromethane (R12) and propane are used to demonstrate the method. The requirements of a new predictive method are given including the criteria for the selection of the two reference fluids used. The accuracy of the predictions depends primarily on the accuracy of the thermodynamic property formulations for the two reference fluids. The results of the calculations used in demonstrating the method show that vapor pressures and saturated liquid densities may be predicted within ±0.05 percent with the available equations for the test fluids.