The dependence on temperature and acentric factor of the attractive term of the Redlich-Kwong equation of state has been modified. A new alpha function is expressed in a generalized form. The new equation allows a good representation of vapor pressure data of a great variety of compounds, as well as thermodynamic properties such as the enthalpy of vaporization and the entropy of vaporization. (C) 1998 Elsevier Science B.V. All rights reserved.