(Liquid + liquid) equilibrium (LLE) data were obtained for the ternary systems of {water + propionic acid (PA) + isopropyl methyl ketone (IPMK)} and of {water + PA + isobutyl methyl ketone (IBMK)} at atmospheric pressure and temperatures (303.15, 313.15 and 323.15) K, respectively. The effect of electrolytes on the LLE data for the ternary systems was also investigated. The results obtained from the experiments showed that the electrolytes studied in this work, i.e., NaCl and KCl significantly affect the solubility of PA in the organic solvents used in the experiments. The results also showed that the distribution coefficients for PA and the selectivity of the solvents in extracting PA, increase in presence of electrolytes in the ternary systems. The tie line data of the ternary systems were correlated using the Othmer-Tobias method. The conventional local composition activity coefficient model, the non-random two liquid (NRTL), was used in correlating the experimental data for the ternary systems. It was concluded from the results that the NRTL model accurately correlates the experimental data of the ternary systems. The results for the binary interaction parameters for the NRTL model are also reported. (C) 2004 Published by Elsevier Ltd.