The enthalpies of mixing of six kinds of aqueous amino acid solutions (glycine, L-alanine, L-valine, L-serine, L-threonine and L-proline) and aqueous 1,2-ethanediol solution and their respective enthalpies of dilution have been measured at 298.15 K using flow microcalorimetry. The experimental data have been analyzed in terms of the McMillan-Mayer formalism to obtain the heterotactic enthalpic interaction coefficients. The heterotactic enthalpic pairwise interaction coefficients, h(xy), have been discussed from the points of view of solute-solute interactions. (c) 2006 Elsevier B.V. All rights reserved.