This paper describes liquid-liquid equilibrium data generated for systems comprising mixtures of tetralin or C-4- or C-6-alkyltetralins with cetane and sulpholane at 60 and 100 degrees C. The alkyltetralins used for these studies were prepared in this laboratory, by Friedel-Crafts alkylation of tetralin, as mixtures of isomeric components. The experimentally generated equilibrium data were predicted by using UNIFAC and correlated by UNIQUAC and NRTL solution models by representing the alkylated tetralins by averaged structures. It was observed that the values predicted by use of these average structure models were in good agreement with experimental results.