The excess molar enthalpy HmE has been determined as a function of mole fraction x at atmospheric pressure and 298.15 K for several mixtures of {a ketone (asymmetrical or symmetrical) + di-n-butyl ether}. The ketone was 2-butanone, 2-pentanone, 2-hexanone, 2-heptanone, 2-octanone, 2-nonanone, 3-pentanone, 4-heptanone, or 5-nonanone. All mixtures showed positive excess molar enthalpies which decreased with increasing chain length of the ketone.