The Mattedi-Castier-Tavares (MTC) equation of state (EOS) is used to model the phase behavior of mixtures whose components interact via strong specific interactions. This is the case of several aqueous and nonaqueous polar mixtures of industrial interest, whose phase behavior may be significantly different from that of ideal mixtures. The MTC EOS is based on the hole-lattice theory, whose partition function is derived from the generalized van der Waals theory. The model uses a region approach to characterize polar molecules and does not introduce terms based on other theories to account for hydrogen bonding. The results of the MTC EOS are generally in very good agreement with experimental results.