This paper presents an improved version of a purely predictive thermodynamic model proposed previously by Coniglio et al. (Fluid Phase Equilib. 1993, 87, 53-88). The main feature of this model is to be based on a Peng-Robinson type equation of state with parameters determined through homogeneous group contribution methods. The new model estimates vapor pressures, saturated liquid densities, heats of vaporization, saturated liquid heat capacities, and speed of sound in saturated liquids of a large number of hydrocarbons within the experimental accuracy, from the triple point to 2 bar. The required inputs for each compound are the molecular structure and the experimental normal boiling point or at least one vapor pressure measurement. The applicability of the new model was verified through prediction of vapor pressures of nonhydrocarbon organic compounds (acids, esters, alcohols,...). The obtained results confirm the reliability of the new model when extrapolating to non-hydrocarbon organic compounds.