Asphaltene precipitation is a serious problem, which can affect oil production and transportation. To avoid this problem, knowledge of asphaltene phase behavior is of great interest. Asphaltene precipitation is traditionally modeled using the Flory-Huggins polymer theory. Two assumptions are normally made: (1) The precipitated phase consists of asphaltene only (2) The precipitated phase consists of asphaltene and nonasphaltene components and the oil phase is free of asphaltene. In this work, the Flory-Huggins theory is employed to develop a monodisperse model in which, a distribution of asphaltene and nonasphaltene components in the oil and precipitated phases is considered. It is shown the previous Flory-Huggins theory based models are specific cases of the present model. The results of the new model are finally compared with some selected experimental data from the literature. (C) 2007 American Institute of Chemical Engineers.