A group contribution method allowing the estimation of the temperature dependent binary interaction parameters (k(ij)(T)) for the widely used Peng-Robinson equation of state (EOS) is proposed. A key point in our approach is that the kij between two components i and j is a function of temperature (T) and of the pure components critical temperatures (T-Ci and T-Cj), critical pressures (P-Ci, P-Cj) and acentric factors (omega(i), omega(j)). This means that no additional properties besides those required by the EOS itself (T-C, P-C, omega) are required. 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, we decided to call this new model PPR78 (predictive 1978, Peng-Robinson EOS). In this paper six groups are defined: CH3, CH2, CH, C, CH4 (methane), and C2H6 (ethane) which means that it is possible to estimate the k(ij) for any mixture of saturated hydrocarbons (n-alkanes and branched alkanes), whatever the temperature. The results obtained in this study are in many cases very accurate and often better than those obtained with the best EOS/g(E) models. In particular, it is shown that asymmetric systems can be accurately predicted with our model. Some comparisons are given with the LCVM model. (C) 2004 Elsevier B.V. All rights reserved.