Solubility and tie-line data were obtained for the ternary system : water + propionic acid + I-butanol at 303.2 K. The 'salting-out' effect was studied by using sodium chloride (NaCl) at three concentrations within its solubility limits. The effect of the addition of this salt on the liquid-liquid equilibrium data of the ternary system has been investigated at the same temperature, determining independently both the solubility curve and the tie lines. In all cases, the addition of salt enhances significantly the distribution coefficients and selectivities, while the region of heterogeneity increases as compared to the no-salt condition. Tie-line data were correlated by the method of Othmer and Tobias [R.E. Othmer, P.E. Tobias, Ind. Eng. Chem. 34 (1942) 690-700.] and their parameters were evaluated. From the experimental results, it is evident that NaCl is not distributed in the same proportion between the phases at equilibrium, and that l-butanol is a good solvent for extraction purposes.