In a previous paper [J.N. Jaubert, F. Mutelet, Fluid Phase Equilib. 224 (2004) 285-304], we started to develop a group contribution method aimed at estimating the temperature dependent binary interaction parameters (k(ij)(T)) for the widely used Peng-Robinson equation of state (EOS). In this approach, the k(ij) between two components i and j is a function of temperature (T) and of the pure component critical temperatures (T-ci and T-cj), critical pressures (P-ci, P-cj) and acentric factors (omega(i), omega(j)). Because our model relies on the Peng-Robinson EOS as published by Peng and Robinson in 1978 and because the addition of a group contribution method to estimate the k(ij) makes it predictive, this model was called PPR78 (predictive 1978, Peng-Robinson EOS). In our previous paper, six groups were defined: CH3, CH2 CH, C, CH4 (methane) and C2H6 (ethane). It was thus possible to estimate the k(ij) for any mixture of saturated hydrocarbons (n-alkanes and branched alkanes), whatever the temperature. In this study, the PPR78 model is extended to systems containing aromatic compounds. To do so, two new groups were added: CHaro and C-aro. (c) 2005 Elsevier B.V. All rights reserved.