The liquid-liquid equilibrium.(LLE) of the ternary system water + acetic acid + butyl butanoate has been determined experimentally at room temperature. The phase diagrams were obtained by determining the solubility and tie-line data. GCEOS, NRTL and UNIQUAC models were used to predict the LLE data with a root-mean-square deviation value of 0.1314, 0.0938 and 0.2955, respectively. The reliability of the experimental tie-line data were obtained by Othmer-Tobias correlation. Distribution coefficient and separation factor were evaluated for the immiscibility region of the ternary system. (C) 2015 Elsevier B.V. All rights reserved.