Mixing enthalpies of aqueous L-serine and L-threonine solutions and aqueous tetrohydrofuran (THF) and 1,4-dioxane solutions and their dilution enthalpies have been determined with a Thermometric-2277 Thermal Activity Monitor at T = 298.15 K. The h(xy) values, obtained with the McMillan-Mayer formalism, for the alpha-amino acids bearing polar side-chain (L-serine and L-threonine) with THF and 1,4-dioxane are compared with values reported in the literature for the alpha-amino acids with non-polar side-group (glycine, L-alanine, L-aminobutyric acid and L-valine) with THF and 1,4-dioxane. The results are interpreted in terms of solute-solute interactions. The group additivity concept by Savage and Wood (SWAG) has also been used. Contributions of each amino acid, functional group have been estimated. (C) 2004 Elsevier Ltd. All rights reserved.