In two phase oil-water dispersed flow, a phase inversion may occur whereby the continuous phase becomes dispersed. This phenomenon which controls the nature of the phase in contact with the pipe has a great importance on the corrosion and on the pressure drop. A model for the phase inversion is presented, it is based on a thermodynamic approach, and it is valid for ail flow regimes. Experimental data from the litterature are used to validate the model. In laminar flow, this approach gives similar results to those obtained by Yeh. For most data, the model agrees well with the experimental data.