The Peng-Robinson equation of state (PR EOS) is used for the prediction of 1-octanol-water partition coefficients (K-OW) and infinite dilution activity coefficients (gamma(infinity)). Unlike the conventional approach where the EOS parameters must be determined from the critical properties and acentric factor of each chemical species in addition to using some mixing rule to account for composition dependence. these parameters are determined here using a solvation model developed based on first principle COSMO calculations. Consequently, this approach, denoted as PR + COSMOSAC, requires input of only molecular connectivity and is capable of describing both temperature and pressure effects in fluid phase equilibria. It is found that the predicted mutual solubility of water and 1-octanol, the partition coefficient K-OW of a third chemical and gamma(infinity) in water are in good agreement with reported experimental data. In response to the 5th fluid challenge, linear correlation equations with the correlation coefficient(R-2) better than 0.96 are developed for highly accurate predictions of properties specifically for alcohols and amines. (C) 2009 Elsevier B.V. All rights reserved.