Excess molar enthalpies, measured at 298.15 K in a flow microcalorimeter, are reported for the ternary mixtures (dibutyl ether + n-hexane + n-heptane) and (dibutyl ether + n-hexane + n-octane). Smooth representations of the results are described and used to construct constant excess molar enthalpy contours on Roozeboorn diagrams. It is shown that reasonable estimates of the excess enthalpies of the present ternary mixtures can be obtained from the model of Liebermann and Fried [Ind. Eng. Chem. Fundam. 11 (1972) 350; Ind. Eng. Chem. Fundam. 11 (1972) 354], using only the physical properties of the components and their binary mixtures.