The enthalpies of solution of 1,4-dioxane in {(1 - x)F + xH(2)O}, {(1 -x)DMF + xH(2)O} and {(1 - x)DMF + xH(2)O} have been measured within the whole mole fraction range at T = 298.15 K. Based on the obtained data, the effect of substituting methyl groups at the nitrogen atom in formamide on the preferential solvation of 1,4-dioxane has been analyzed. A simple model has been proposed to describe the influence of structural and energetic properties of the mixed solvent on the energetic effect of hydrophobic hydration and preferential solvation of 1,4-dioxane by the components of the examined mixture. (c) 2006 Elsevier Ltd. All rights reserved.