Equilibrium tie line data have been determined at 323.15 K, 348.15 K, and 373.15 K for the ternary liquid-liquid equilibria (LLE) of octane + (benzene or toluene or m-xylene) + sulfolane systems. The relative mutual solubility of benzene is higher than that of toluene or m-xylene in octane + sulfolane mixtures, The tie line data were correlated with the NRTL and UNIQUAC models. The calculated values based on the NRTL model were found to be better than those based on the UNIQUAC model; the average root-mean-square deviation between the phase composition obtained from experiment and that from calculation was 0.49 for NRTL compared to 0.53 for UNIQUAC. The values of selectivity and the distribution coefficient were derived from the equilibrium data at different temperatures.