A new and rigorous method for the fractional description of solvation and transfer free energies is presented. The method is based on the use of the Miertus-Scrocco-Tomasi self-consistent reaction field method (MST-SCRF), and allows for a rigorous partition of the total solvation free energy into surface elements. The method gives a complete picture of the hydrophobicity/hydrophilicity of molecules. Present results allow us to expect that the method might provide useful information in drug design and molecular modeling studies.