Free energies of solvation of chlorophenols were calculated in two solvents: water and n-hexadecane from the AMSOL program. These free energies of solvation are the sum of two terms: polarization free energies (delta GENP) and cavity, dispersion, solvent structure free energies (G degree CDS). This study shows, in the case of chlorophenols, that a direct relation exists between one of the two components for the calculation of free energy (G degree CDS) in water and n-hexadecane, and the ecotoxicity values for five biological systems. We point out the interest of using these new descriptors in QSAR study.