The three-contribution electrolyte NRTL model [1] with an additional term of Bronsted-Guggenheim type is applied to represent the liquid-liquid equilibrium (LLE) in mixed-solvent electrolyte systems. The Bronsted-Guggenheim term compensates for the inadequacies of the Debye-Huckel and Born equations when they are extended to mixed-solvent electrolyte systems. Attention is given to the definition of reference and standard states. The importance of the electrolyte solution chemistry is emphasized. The extended electrolyte NRTL model is compared with the Zerres-Prausnitz model [2] on correlation of LLE data for four ternary aqueous-organic solvent electrolyte systems.