In this work, experimental tie-lines at isothermal conditions are reported for the ternary system (water + tetrahydrofuran + methylcyclohexane). The data were determined at five temperatures (278.15, 288.15, 298.15, 323.15, and 343.15) K and atmospheric pressure in order to show the influence of temperature on the phase behavior of this system. The complete phase diagrams obtained at temperatures from (278.15 to 323.15) K are of type 1. The experimental data were correlated using the NRTL, UNIQUAC, and extended UNIQUAC thermodynamic models by minimizing the differences between the experimental and calculated mole fractions of the two liquid phases in coexistence. The calculated mole fractions were obtained through the minimization of the Gibbs energy of the system along with thermodynamic stability tests to find the most stable state of the system. Results of the representation showed that the extended UNIQUAC model is superior to the NRTL and the original UNIQUAC models in correlating the (liquid + liquid) equilibrium data of the (water + tetrahydrofuran + methylcyclohexane) system over the temperature range studied. Predicted phase diagrams with the extended UNIQUAC model for this ternary system showed that they are of type 1 at temperatures from (278.15 to 298.15) K and of type 2 at 323.15 K and higher temperatures. (C) 2014 Elsevier B.V. All rights reserved.