This paper presents an intensive revision of the application of the extended real association solution (ERAS) model for binary mixtures containing one or both self-associating compounds. We suggest new definitions for the complexation constant K-AB and for the Flory's parameter X-AB, which involve a symmetrization of the model with respect to the change A <---->, B in addition to endow these parameters with a clearer physical meaning. The new expresions for KAB and XAB also imply an extension of the model for application to any binary mixture exhibiting cross-association regardless of the relative degree of self-association of the components. A critical review on the formulation and application of the model is performed in order to clarify several disagreeing points in papers related to this matter.