Enthalpies of dilution of glycine, L-alanine and L-serine in aqueous ethylene glycol solutions have been measured at 298.15 K by a mixing-flow microcalorimeter. The homogeneous enthalpic interaction coefficients of the three zwitterions have been computed by least-squares fitting on the basis of the McMillan-Mayer theory. The variations of the enthalpic pairwise interaction coefficients with the mass fraction of ethylene glycol in mixtures are interpreted in terms of solute-solute and solute-solvent interactions.