The cubic equation of state (EoS) of Patel and Teja with a new mixing rule, which is based on the assumption that the excess Helmholtz energy at infinite pressure is zero, was presented to calculate the vapor-liquid equilibria of highly asymmetric systems. With only one temperature-independent parameter, the new mixing rule was tested with various binary and ternary asymmetric systems and better results were obtained for this new mixing rule compared to the MHV1, LCVM and van der Waals mixing rules. (C) 2004 Elsevier B.V. All rights reserved.