A method for estimation of the phase equilibrium, density, enthalpy, heat of vaporization and molecular weight of refrigerant/oil solutions (ROS) is proposed in this paper. The method is based on the theory of thermodynamic similarity, since refrigerant/oil solutions appear to be thermodynamically similar in the region of the refrigerant mass concentrations: 0.3 less than or equal to w(R) less than or equal to 1.0. The initial information is the concentration dependence of the temperature of the normal boiling point, the concentration dependence of the density in very narrow temperature ranges, and the temperature dependence of the isobaric heat capacity of the liquid phase of the pure oil. On the basis of this information, the proposed method allows calculation of all the above-mentioned properties. Modeling of thermodynamic properties of the ROS requires data on pseudocritical properties and molar weight. Hence, the method of estimation of these properties is proposed. (C) 2003 Elsevier B.V. All rights reserved.