Liquid-liquid equilibria (LLE) for the ternary system water + acetic acid + cyclohexanone was studied at (293.2-323.2) K and at atmospheric pressure. The immiscibility region was found to be relatively small and not sensitive to the change of temperature. The Othmer-Tobias equation and the Bachman equation were both used to check the reliability of the obtained experimental tie-line data. The experimental results were correlated with both the NRTL and the UNIQUAC activity coefficient models. The calculated results showed good agreement with the experimentally determined ternary LLE data. The root mean square deviations (RMSD) obtained by comparing the calculated and experimental two-phase compositions are 0.72% for the UNIQUAC model and 0.40% for the NRTL model. The obtained interaction parameters can be used in the calculation of LLE for the ternary system water + acetic acid + cyclohexanone as well as for the design and optimization of the related separation process. (C) 2014 Elsevier B.V. All rights reserved.