Molar excess Gibbs free energies of mixing (CE) for butyl acetate+cyclohexane or benzene or toluene or o- or m- or p-xylene were calculated by using Barker’s method from the measured vapor pressure data by static method at 308.15±0.01 K over the entire composition range. The GE values for the binary mixtures containing cyclohexane or benzene are positive; while these are negative for toluene, o-, m- and p-xylene system over the whole composition range. The GE values of an equimolar mixture for these systems vary in the order: cyclohexane>benzene>o-xylene>m-xylene>p-xylene>toluene. The GE values for these systems were also calculated by Sanchez and Lacome theory using the previously published excess enthalpy and excess volume data. It is found that while values of GE from Sanchez and Lacombe theory are in reasonably good agreement with those calculated by Barker method for m-xylene and pxylene mixtures, agreement is very poor for other systems although they predict the sign of GE data except in the case of mixtures containing benzene.