The research conducted here was an attempt to use the currently available activity coefficient methods with universal sets of parameters to simultaneously predict binary and ternary vapor-liquid and liquid-liquid equilibrium data. Literature studies available with such correlations based on two-parameter models (UNIQUAC and LSG) and three-parameter models (NRTL and GEM-RS) used different binary interaction parameters to calculate vapor-liquid and liquid-liquid equilibrium data. The focus of this research was to predict phase equilibrium data (binary mutual solubility (BMS), infinite dilution activity coefficient (gamma(infinity)), binary vapor-liquid equilibrium (VLE), distribution coefficient (D-sw), and ternary liquid-liquid equilibrium (LLE)) within fair error using only a single set of parameters obtained from the above-mentioned models regardless of vapor-liquid or liquid-liquid equilibrium. This was proven by an investigation of the hexane-butanol-water ternary system, in which hexane-butanol, hexane-water, and water-butanol binary LLE data, binary VLE data, and gamma(infinity) data were used to analyze the ternary system. Ternary LLE data of the hexane-butanol-water system were also analyzed. In each of the mentioned binary systems and the ternary system, the calculated and experimental data were compared. The results of this analysis predicted binary mutual solubility data, binary VLE data, ternary LLE data, gamma(infinity), and D-sw concurrently within reasonable error (<= 15%).