The characterizations of the ternary phase diagram and the metastable zone width are important issues for enantioseparation by crystallization procedures. In this work, a systematic study of the solubility and metastable zone width data of L-methionine, DL-methionine, and different mixtures of the enantiomers in water as solvent was performed. The eutectic composition in the chiral system in the presence of the solvent as an important characteristic for enantioselective crystallization was determined in the temperature range between (1 and 60) degrees C. A significant shift of this composition was observed.