Mixing enthalpies of aqueous L-valine and L-threonine solutions with aqueous sorbose solution and aqueous fructose solution and their dilution enthalpies have been determined with a Thermometric-2277 thermal activity monitor at 298.15 K. The experimental data have been analyzed in terms of McMillan-Mayer formalism to obtain the enthalpic virial coefficients for heterotactic interaction. The enthalpic pairwise interaction coefficients h(xy) of L-valine with saccharides are positive and those of Lthreonine are negative. The variations of the enthalpic pairwise interaction coefficients are interpreted in terms of solute-solute interactions.