Phase equilibrium in binary mixtures found in wine and must distillation processes have been analyzed using equations of state and models for activity coefficients. In wine and must distillation the presence of polar substances found in the mixture to be distilled and the very low concentration of many components (different from ethanol and water), called congeners, make it difficult to model these mixtures, for simulation and design purposes. In this study, two liquid-phase models, NRTL and UNIFAC and a predictive equation of state, the PSRK equation, have been used. Nine binary ethanol + congener mixtures and nine binary water + congener mixtures have been considered for analysis. The congeners used in this study are considered as legal compounds by the Chilean legislation for the production of a spirit called Pisco. Comparison with available literature data is done. Conclusions on the accuracy of the models used in the study are drawn and recommendations on which models should be considered in these situations are given. (C) 2004 Elsevier Ltd. All rights reserved.