Experimental liquid-liquid equilibrium (LLE) of the water-acetic acid-sec-butyl acetate ternary system was investigated at 298.15, 303.15, 308.15 and 313.15K and at atmospheric pressure. Separation factors were also evaluated for the immiscibility region. The NRTL and UNIQUAC models were applied to fit the experimental data for the ternary system. The binary interaction parameters obtained from both models were found to be successfully correlated with the equilibrium compositions. The UNIFAC group contribution method was employed to predict the observed ternary LLE data. It was found that four types of the UNIFAC model (UNIFAC, UNIFAC-LL, UNIFAC-DMD, and UNIFAC-LBY) did not provide a good prediction of the LLE data for this ternary system. (C) 2010 Elsevier B.V. All rights reserved.