Using data for heats of mixing h(E), the temperature-dependent parameters of the NRTL model have been estimated for 55 systems of binary liquid mixtures. In order to test the model thoroughly, systems of various types, including associating and partially miscible systems that have data for h(E) at more than one different isotherm, are considered. The temperature dependence for the parameters of the model is assumed to be linear. The physical meanings and non-uniqueness of the parameters are discussed. Later these parameters are employed to predict the heats of mixing, partial molar heats of mixing and activity coefficients at infinite dilution. In previous studies, the same properties were predicted by assuming a non-linear temperature dependence for the parameters of the NRTL model. Hence the performance of the model is tested by comparing the predictions with experimental values when the linear and non-linear temperature dependences of the parameters are introduced into the model.