A new method tor estimation of parameters in cubic equations qfstatefirom ab initio Solvatioti calculations is presented. hi this n7ethod, the tcniperature-delmndent intercietion parameter a(T) is determinedfrom the attractive component of'solvationfree energy, ivhereas [lie volume parameter b is assumed to be th(It Ql'solvation cavity. This method requires only eleinent-spec fic parameters, i.e., atomic radius and disI)ersion coefficient, and nitic universal parameters for electrostatic and hydrogen-bonding interactions. The equations ofstate (EOS) parameters so deterinitied allow the descril)tion (?I'the cony)lete fluid phase dial,,ram, including the critical point. We have e-varnined this n7ethod using the Peng-Robinson EOSftw 392 compounds and achieved au accuracy of 43% in val)or pressure, 17% in liquid deHSitY, 5.4% in critical tem1mrature, 11% in critical pressure, and 4% in critical volume. This method is, in princij)le, apl)licable to aHV chemical species and is especiaHy useftd Jbr those whose e_vperimental data are not available. (c) 2008 Arnerican Institute of Chernical Engineers.