The concentration dependent surface area parameter (CDSAP) model is applied to correlate the vapor-liquid equilibria for binary systems and liquid-liquid equilibria for ternary systems containing 1-butanol + water. The model is based on the quasi-chemical theory. The surface area parameters in the model depend on partner molecules and concentrations. The activity coefficients of multi-component systems can be calculated with the binary parameters of constituting binary systems. The advantage of the model is that the liquid-liquid for ternary systems and the vapor-liquid equilibria for constituting binary systems are calculated well with the same parameter set. The parameters in CDSAP model are explained by functions of temperature to apply in wide range of temperature. The calculated results by CDSAP model are almost the same as those by NRTL and UNIQUAC models for the vapor-liquid equilibria of binary systems, and better than those by NRTL and UNIQUAC models for the liquid-liquid equilibria of ternary systems containing 1-butanol + water. (C) 2013 Elsevier B.V. All rights reserved.