Methods are presented for selecting values of chemical properties of vapor pressure, water solubility, Henry's law constant, and octanol—water and octanol—air partition coefficients, which are subject to thermodynamic constraints, while taking advantage of all measurements. The aim of the mathematical procedures is to find the one set of internally consistent partitioning parameters that is minimally divergent from the experimental values. Information about the reliability or uncertainty of reported values can be accounted for by weighing factors. A similar approach is applied to the temperature dependence of these properties. The influence of partial miscibility of the octanol—water system is discussed and a correction is suggested for this effect. The selection method is applied to 50 mostly aromatic chemicals for which multiple measured partitioning data are available. The resulting sets of consistent property data are presented and discussed.