The excess molar Gibbs energies of mixing for (2-methylpropan-2-ol + benzene, or toluene, or o-, or m-, or p-xylene) at T = 308.15 K have been calculated by the Barker method from vapour pressure data measured by the static method. The Gibbs energies of mixing for these binary systems are also analysed in terms of the Mecke-Kempter type of association model with a Flory contribution term using two interaction parameters.