This work shows the experimental values obtained for H-m(E) and V-m(E) at the temperature of 298.15 K and atmospheric pressure, for a set of 20 binary mixtures comprised of the first four butyl esters (methanoate to butanoate) with five alpha,omega-dibromoalkanes (1,2-dibromoethane to 1,6-dibromohexane). The H-m(E) are endothermic for mixtures with butyl methanoate, while for the other esters the H-m(E) adopt a sigmoidal shape, The V-m(E) are positive for mixtures with low molecular weight dibromoalkanes, becoming negative with contractive effects in the final mixture, as the dihalide chain increases. The results indicate that the mixtures present specific interactions, with simultaneous expansion/contraction and exothermic/endothermic effects, and an explanation is given for the different types of interaction taking place. Experimental data are correlated with a polynomial equation used in previous works with satisfactory results. Modelling of the experimental results of the mixtures is carried out on the H-m(E) values, giving rise to an adequate definition of the different interactions taking place. Two versions of the UNIFAC method were used, and for Dang and Tassios' version different possibilities were considered for the interaction parameters of the ester (G)/dibromide (G'). The best estimations were obtained when the pair of interaction parameters, type a(G/G'), depended on the number of carbon atoms in the compounds constituting the mixture. (C) 2009 Elsevier Ltd. All rights reserved.