Precipitation of heavy organics, especially asphaltenes, causes many problems in oil industry. Thermodynamic models are used in order to realize the phase behavior of asphaltene deposition. In this study, the Association Equation of State (AEOS) model was developed for predicting asphaltene precipitation in crude oil. In addition to a physical term, a chemical term was used in this model to consider the association nature of asphaltene. The result of this model was compared to experimental data of three live oils and the results of other models. The results showed good accuracy of this model in comparison with the other models. (C) 2011 Published by Elsevier Ltd.