The original UNIFAC model and two of its modifications have been fitted to binary molar excess enthalpy (H(E)) data to correlate and predict binary excess enthalpy H(E) in systems containing esters and n-alkanes. The results show that the version of Rupp et al. (Ind. Eng. Chem. Process Des- Dev., 23 (1984) 391) and the UNIFAC model with tripled values of surface area parameters (UNIFAC(3Q)) are preferable to the original UNIFAC model. Both versions produce mean deviations of H(E) better than 7% for all the systems containing methanoates, ethanoates, the other alkanoates and benzoates studied.