The interaction of ascorbic acid and some monofatty acid ascorbyl esters to bovine serum albumin was investigated by a dynamic dialysis method in an attempt to elucidate some of the structural specificities of the interaction. The chemicals used were ascorbic acid, ascorbyl octanoate, ascorbyl decanoate, and ascorbyl benzoate. Analysis of the binding data showed that the albumin possesses a single binding site for these chemicals, and that there are marked differences in their binding strength, which increases in order of ascorbic acid, benzoate, octanoate, and decanoate. The affinity of binding was also found to depend on the hydrophobic character of their acid residues, as expressed by a partition coefficient. The thermodynamic parameters indicate that these interactions are exothermic and occur spontaneously under the experimental conditions used. In addition electrostatic attraction, the interaction of hydrophobic groups between the protein and ascorbates was shown to be involved in the formation of complexes. Finally, the role of the hydrophobic interaction was indicated from the consideration of values for the positive change of entropy.