Asphaltenes flocculation is described as a thermodynamic transition inducing the formation of a new liquid phase with a high asphaltenic content; this phase being the asphaltenic deposit. The thermodynamic model selected is the Peng-Robinson Equation of State associated with the Abdoul and Peneloux group contribution mixing rules. The oil is modeled by 33 pseudocomponents. Mainly, the heavy F11+ residue is represented as one pseudocomponent for the F-11-F-20 cut and as 4 pseudocomponents for the F20+ cut: "Sat F20+", "Aro F20+", "Resins" and "Asphaltenes". The physical properties of the "Sat F20+", "Aro F20+" and "Resins" pseudocomponents are calculated using the group contribution methods of Avaullee, and of Rogalski and Neau, based on the knowledge of their molecular structure. The physical properties of the "F-11-F-20" and "Asphaltenes" pseudocomponents are fitted in order to reproduce correctly the bubble pressure, the relative volumes and the flocculated quantities at 303 K. The model gives the proportion and the composition of asphaltene deposits in the oil at different temperatures (303-403 K) within a relatively large pressure range (0.1-50 MPa) including the bubble pressure of the considered crude.