A simple modification of the NRTL equation is proposed which consists of inserting the ratio of the molar volumes of the pure compounds as a multiplying factor of the binary parameters G(ij) and G(ji). The suitability of this modification is evaluated by following two procedures in order to correlate or to predict the VLE of several binary systems taken from the literature ranged according their non-ideality degree, namely the prediction of the VLE data assuming the geometric mean g(ij) = (g(ii)(.)g(jj))(0.5) for the energy interaction parameter related to the i-j interactions; the correlation of the above data according to the NRTL equation written in the one-parameter form, as suggested by Tassios. The modified NRTL equation appears significantly more reliable than the NRTL in its classical form in both cases. As a rule, the improvement is more relevant the higher is the non-ideality of the considered system.