Experimental liquid-liquid equilibrium (LLE) data for the system of (water + propionic acid + iso-butyl acetate) were obtained at T=(298.2, 303.2, 308.2, and 313.2) K and atmospheric pressure. This ternary system exhibits type-1 behavior of LLE. The experimental tie-line data were correlated using the UNIQUAC and NRTL models. The reliability of the experimental tie-line data was determined by applying the Othmer-Tobias and Hand correlations. Distribution coefficients and separation factors were calculated over the immiscibility regions. The influence of temperature on the equilibrium characteristics and separation factor was found to be minor at the temperatures studied. The average rmsd values between the observed and calculated mass fractions were 0.92% and 0.98% for the UNIQUAC and NRTL models, respectively. The thermodynamic models showed good agreement to the experimental results. (C) 2012 Elsevier B.V. All rights reserved.