Liquid-liquid equilibrium data were measured for the ternary systems water + ethyl acetate + diethyl succinate and water + acetic acid + diethyl succinate at 298.15 K and atmospheric pressure. The reliability of the experimental data was confirmed using the Othmer-Tobias correlation. Vapor-liquid equilibrium data were also measured for the binary systems ethyl acetate + diethyl succinate at 313.15 K. acetic acid + diethyl succinate at 323.15 K and ethyl acetate + ethanol at 101.325 kPa. Binary parameters for the modified UNIQUAC and NRTL equations were obtained by fitting experimental and reported data using the regression tool in Aspen Plus (R). The Hayden-O'Connell equation was used to represent interactions in the vapor phase. The models agree reasonably well with the experimental data and can predict reported azeotropic conditions. (C) 2009 Elsevier B.V. All rights reserved.