The accurate isobaric separation of multicomponent mixtures by distillation require reliable vapour-liquid equilibrium data. For non-ideal liquid-phase behaviour, there is a need to use a predictive model for the liquid-phase activity coefficients since the experimental determination of multicomponent vapour-liquid equilibrium data is laborious and time consuming. The estimated vapour-phase compositions are dependent on the predictive thermodynamic method used. The abilities of Wilson and UNIQUAC equations in the prediction of isobaric binary and ternary vapour-liquid equilibria were compared in this paper. The ternary systems, Ethanol-Benzene-Heptane and Hexane-Ethanol-Benzene which have highly non-ideal liquid-phase behaviour and provide binary azeotropes have been chosen to study in this work. UNIQUAC Eq. was found to be little superior in the prediction of ternary vapour-liquid equilibria with mean deviations ranging from 0.0146-0.0334 whereas the Wilson Eq. could predict the ternary vapour compositions within the accuracy of 0.0158-0.0333.