Methods were developed for estimating the equilibrium sorption behavior of hydrophobic pollutants. At low pollutant concentration (aqueous phase concentrations less than half the solubility), sorption isotherms were linear, reversible, and characterized by a partition coefficient, K(p). Partition coefficients normalized to organic carbon, K(oc)(K(oc)=K(p)/fraction organic carbon), were highly invariant over a set of sediments and soils collected from throughout the nation. Equations for estimating K(oc) from water solubility (including crystal energy) and octanol/water partition coefficients were developed. The predictive equations were tested on literature sorption data and found to estimate measured K(oc)'s generally within a factor of two.