The group interaction parameters for modified UNIFAC (Dortmund) of the newly defined amine group at cycloaliphatic hydrocarbon occurring for example in cyclohexylamine with six established groups were determined using binary data available from literature and new experimental data presented in this paper. The calculations of binary and ternary systems are compared to the predictions using the amine group at aliphatic hydrocarbon. The liquid-liquid and vapour-liquid equilibria of the quaternary system water + toluene + aniline + cyclohexylamine were determined at two temperatures, each, and predicted with mod. UNIFAC (Do) using the new group interaction parameters. Furthermore, the predictions for the ternary and quaternary systems with mod. UNIFAC (Do) are compared to the predictions with NRTL. UNIQUAC, and Elliott-Suresh-Donohue equation of state using binary interaction parameters. (C) 2011 Elsevier B.V. All rights reserved.