A detailed analysis on the capability of the NRTL model to describe W-shaped excess heat capacities c(p)(E) of binary mixtures is presented. P Both the classical and crossover renormalized versions of the model are used to correlate experimental data for various polar+ alkane systems. The results are analyzed and discussed after a careful description of the fitting strategies. The classical version allows a good thermodynamic description far away from the critical point to be obtained. It also provides a significant insight into the relation of c(p)(E) and the non-randomness of the molecular distribution in the mixture. On the other hand, the crossover-renormalized version qualitatively represents the behaviour of c(p)(E) both near the critical point and away from it; however, it exhibits some deficiencies from a quantitative point of P view. (c) 2005 Elsevier B.V. All rights reserved.