The caseinomacropeptide (CMP) is a bioactive peptide produced during cheese making. It is found in abundance in whey. CMP aqueous solutions allow the incorporation of large amounts of CaCl2 but the mechanism of calcium-CMP interactions are unknown. In order to evaluate its calcium binding capacity, the following techniques were performed: Dynamic Light Scattering (DLS), Fourier Transform Infrared spectroscopy (FTIR), dialysis, conductivity, precipitation of CaCl2/CMP complex by ethanol, electrochemical Ca2+ binding isotherms, and inhibition of calcium phosphate precipitation. One mole of CMP can bind 9mol of calcium, and the CMP self-assembles as a hexameric form. A model is proposed to explain the CMP self-association in presence of CaCl2. All rights reserved, Elsevier.