A detailed cartography of the maximal Pyrenean deformation dated from Eocene has been made for the northern Bay of Biscay from the interpretation of new reflection seismic data. These new seismic images confirm the occurrence of a primary tectonic event for the Pyrenean phases. This event would underline the initialisation of the Iberia/Europe convergence. The Pyrenean deformations are mainly located at the boundaries of the continental and oceanic domains and affect the oceanic crust. This deformation is principally underlined by compressive and inversed structures.