The enthalpies of mixing of systems formed from alcohols (methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and 2-butanol) and sunflower oil at 298.15 K are presented. Enthalpies were measured in the composition range in which the compounds were miscible. From the experimental measurements, we calculated the heat capacities of the mixtures. Several group contribution models were applied to estimate the enthalpies of mixing of these mixtures. The average deviations varied from 10 to 60%, depending on the model and compound. The best prediction in all cases was the Nitta model, with average deviations from 10 to 30%. The novelty of the work is that models of this type have not been applied previously to predict enthalpies of such large molecules, and the results of the estimates are of the same order as other types of compounds (pure compounds of small size).Recently, we have been interested mainly in studying the mixing properties of mixtures involving organic solvents with vegetable oils (1-8). The present work is part of a series in which enthalpies of mixing of the mentioned compounds are measured. When experimental data are missing, group-contribution methods can be successfully applied to predict important properties such as enthalpies, vapor-liquid equilibria, and density. In groupcontribution methods, it is assumed that the mixture consists not of molecules but of functional groups. Different group-contribution methods, such as the analytical solution of groups (ASOG) (9) and universal quasi-chemical functional group activity coefficients (UNIFAC) (10), have been suggested. In both methods, the required activity coefficient is calculated by a combinatorial and a residual part. The UNIFAC method shows some weakness because poor results are obtained with compounds that are very different in size. To eliminate most of the mentioned weaknesses, some modifications of the UNIFAC method have been developed [see Dang and Tassios (10), Larsen et al. (11), and Weidlich and Gmehling (12)]. The UNIFAC group-contribution model was originally developed by Fredenslund et al. (13) using the universal quasi-chemical (UNIQUAC) equation by Abrams and Prausnitz (14). The activity coefficients in this model are calculated as the addition of two terms. The first one is combinatorial and takes into account the differences in shape and size of the molecules. The second one is a residual term describing the energetic interactions present in the mixture. The adjustable parameters in this model are the energetic interaction parameters between groups. Dang and Tassios (10) modified the original model, and their version is focused only on excess molar enthalpy estimations. In the version of Larsen et al. (11), the interaction parameters become temperature dependent, and the combinatorial term is modified. As a result, this version can predict other properties, such as Gibbs potential and phase equilibria. Weidlich and Gmehling (12) also modified the temperature dependence of the parameters, recalculated interaction parameters usi...