A molecularly explicit property prediction mode (MEPP) is developed for predicting the properties of light petroleum fractions from ASTM D86 distillation data. The method uses a molecularly-explicit characterization model (MECM) based on optimization to define the molecular composition of the petroleum fuel from which more than 20 thermodynamic and transport properties are calculated. The model is tested using a set of 68 pure components to characterize and predict the properties for 30 different petroleum naphtha samples and is found to be in excellent agreement with the cur-rent conventional prediction methods based on global properties. The method is suitable for incorporation into the new generation of molecularly-explicit models for simulating the kinetics and dynamics of petroleum refining processes and has the flexibility to be tailored to use any set of pure components as desired. (C) 2005 Elsevier Ltd. All rights reserved.