Excess molar enthalpies for the ternary system {x(1) methyl tert-butyl ether (MTBE) + x(2) (1-pentanol) + (1 - x(1) - x(2)) nonane} and the involved binary mixtures {x methyl tert-butyl ether + (1 - x) nonane} and, {x (1-pentanol) + (1 - x) nonane} have been measured at the temperature of 298.15 K and atmospheric pressure over the whole composition range. Values of excess molar enthalpies were measured using a Calvet microcalorimeter. The results were fitted by means of different variable degree polynomials. In the present work, we propose a new expression to fit the ternary excess molar enthalpy, which takes into account the asymmetric shape of the three binary systems. The group contribution model of the UNIFAC model (in the versions of Larsen and Gmehling) was used to estimate ternary excess enthalpy values. Several empirical expressions for estimating ternary properties from binary results were also tested. (c) 2005 Elsevier B.V. All rights reserved.