This work reports the phase behavior of the ternary system ethanol + water + methanol at 101.3 kPa. Prediction of activity coefficients and equilibrium compositions with different UNIFAC group contribution models showed poor agreement. Consistency of experimental data was tested by the McDermott-Ellis method. 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.