The results of this investigation have shown that with the use of high resolution NMR relaxation measurement studies, some insight into the importance of molecular binding of p,p'-DDA with BSA and HSA may be obtained. The binding phenomena may be interpreted in terms of preferential stabilization of the aromatic rings by binding sites on the BSA and HSA molecules. This was demonstrated by the greater relaxation rates found for the aromatic protons of the p,p'-DDA than those of the alpha-methine proton. These relaxation rates were quite pD dependent as would be expected from a specific binding mechanism. The binding of p,p'-DDA.BSA and p,p'-DDA.HSA is hydrophobic in nature since a direct relationship was found with ionic strength and relaxation times. The relaxation rates of both complexes increase with decrease in temperature.