In the same way as in other processes, the simulation of the distillation of wine and must is a challenging task due to of the lack of thermodynamic information because of scarcity of accurate studies of phase equilibria. Simulation of these processes is rather complicated because of the presence of polar substances (called congeners) at very low concentration. These congeners are essential enological components of the organoleptic matrix, so the availability of accurate studies and quality data is of primary interest. This work studies the phase behaviour of the ternary system ethanol+water+1-pentanol at 101.3 kPa, being the third compound one of the most important legal congeners in common alcoholic distillation. Experimental results showed that this system is partially miscible and exhibits two binary minimum azeotropes. Prediction of activity coefficients and equilibrium compositions with different UNIFAC group contribution models showed poor accurate results. Consistency of experimental data was tested by the McDermott- Ellis method. In addition, available literature was compared and commented upon. The lack of experimental data in multicomponent alcoholic distillation mixtures and the low reliability of the group contribution methods suggest a prudent work into simulation of this kind of distillation processes.