The knowledge about the interfacial properties of ternary liquid mixtures can be used for optimization of extraction processes. While the interfacial tension is experimental accessible, the interfacial concentration profiles can not be measured. In this paper a modified version of the density-gradient theory for ternary systems is applied. The liquid-liquid equilibrium and the grand thermodynamic potential are calculated with the model of Flory and Huggins combined with Koningsveld-Kleintjens model for the activity coefficients. This approach allows the prediction of the interfacial tension and the interfacial concentration profiles of ternary systems based on information of the binary subsystems. The selected ternary system contains two binary subsystems having a miscibility gap, namely water + benzene + butan-1-ol. The predicted interfacial tensions were very close to the experimental data taken from the literature. The theoretical framework predicts an enrichment of butan-1-ol in the interface. (C) 2014 Elsevier B.V. All rights reserved.