Solution densities have been determined for aqueous solutions of the tripeptides of sequence glycyl-X-glycine, where X is one of the amino acids serine, threonine, asparagine, glutamine, cysteine, histidine, and tyrosine, at T = (288.15, 303.15, and 313.15) K. These solution densities were used to calculate the partial molar volumes at infinite dilution, V degrees(2), for the tripeptides. The V degrees(2) results were combined with those determined in previous work for T = 298.15 K to obtain the partial molar isobaric expansions at infinite dilution, E degrees(2) {E degrees(2) = (partial derivative V degrees(2)/partial derivative T)(p)}, for the tripeptides at T = 298.15 K. The contribution of amino acid side-chain hydration to the E degrees(2) results has been discussed.