Assimilation of Argo float trajectories (350m parking depth) in a high resolution model of the Mediterranean Sea has been performed to test the importance of this type of data for operational systems. Starting from a state corresponding to the 28th year of the simulation, two experiments were performed, one with assimilation and one without, during three months in winter 2005. Four Argo floats released in the context of the MFSTEP project are used. The results are very encouraging, showing significant and consistent changes in the ocean circulation. Comparison with independent data of transport through the Channel of Corsica indicates that the results are more realistic with assimilation, showing a non negligible impact of the assimilation process on the large scale circulation of the basin.