(Liquid-liquid) equilibrium data for the ternary systems [water + formic acid or acetic acid or propionic acid + cumene (2-phenylpropane, isopropylbenzene)] at 298.15 K are reported. Complete phase diagrams were obtained by determining solubility and the tie-line data. The reliability of the experimental tie-lines was determined through the Othmer-Tobias plots. Distribution coefficients and separation factors were evaluated for the immiscibility region. The tie-line data were compared with the results predicted by the UNIFAC method. (c) 2006 Elsevier B.V. All rights reserved.