Excess molar enthalpies for the ternary system {x(1) 2-methoxy-2-methylpropane + x(2) ethanol + (1 - x(1) - x(2)) decane} and the involved binary mixture {x ethanol + (1 - x) decane} have been measured at the temperature of 298.15 K and atmospheric pressure, over the whole composition range. No experimental excess enthalpy values were found in the currently available literature for the ternary mixture under study. The results were fitted by means of different variable-degree polynomials. Smooth representations of the results are presented and used to construct constant excess molar enthalpy contours on Roozeboom diagrams. The excess molar enthalpies for the binary and ternary system are positive over the whole range of composition. The binary mixture {x ethanol +(1 - x) decane} is asymmetric, with its maximum displace toward a high mole fraction of decane. The ternary contribution is also positive, and the representation is asymmetric. (c) 2010 Elsevier B.V. All rights reserved.