In a previous work (Coniglio et al. Ind. Eng. Chem. Res. 2000, 39, 5037-5048), a cubic group-contribution- (GC-) based equation of state (EOS) was developed for heavy hydrocarbons. Estimations of various thermophysical properties were obtained within the experimental accuracy from the triple point to 2 bar. The required inputs are the molecular structure of the compound and the experimental normal boiling temperature (Tb) Or at least one vapor pressure measurement. This work presents a new GC method for estimating Tb values suitable for the cubic GC-based EOS of Coniglio et al. in order to obtain a purely predictive thermodynamic model. The performance of this purely predictive model is very satisfactory for all of the thermophysical properties investigated. Furthermore, excellent agreement between the Tb values estimated by the proposed GC method and experimental data (whenever available) is observed.