(Liquid + liquid) equilibrium (LLE) data for (water + propionic acid + dimethyl phthalate) were measured under atmospheric pressure and at T = (298.2, 303.2, 308.2 and 313.2) K. Phase diagrams were obtained by determining solubility and tie-line data. The LLE data of the ternary systems were predicted by UNIFAC method. Distribution coefficients and separation factors were evaluated over the immiscibility regions. (c) 2004 Elsevier Ltd. All rights reserved.