Liquid-liquid equilibrium (LLE) data of water + acetic acid + dimethyl adipate have been determined experimentally at 298.15, 308.15 and 318.15 K. Complete phase diagrams were obtained by determining binodal curve and tie-lines. The reliability of the experimental tie-line data was confirmed by using the Othmer-Tobias correlation. UNIFAC and modified UNIFAC models were used to predict the phase equilibrium in the system using the interaction parameters determined from experimental data of CH2, CH3COO, CH3, COOH, and H2O functional groups. Distribution coefficients and separation factors were evaluated for the immiscibility region. © 2004 Elsevier B.V. All rights reserved.