Briançonnais units are squeezed between two Mesozoic eclogitic belts (Piemont-Ligurian ocean and Valaisan ocean) along the ECORS-CROP seismic line in the Italian-French Western Alps (France, Italy). The metamorphic evolution of this area plays a key role for understanding the evolution of the Western Alps and is discussed on the basis of detailed petrographic investigations carried out on weathered sediments issued from the erosion of the Hercynian belt, especially on lower Permian to Mesozoic sediments. In the Zone Houillère, as well in the Permo-Triassic cover of the Briançonnais basement, the index metamorphic mineral assemblage is mainly composed of white micas with varying chemical composition, chloritoid and garnet. This same assemblage occurs within different lithologies (metaarkose, metapelite, metasandstone). Consequently, equilibrium phase diagrams were computed for different whole rock compositions using DOMINO software. The results of the P-T investigations clearly show that each unit underwent a different sequence of metamorphic reactions. An increase in metamorphic grade from greenschist facies conditions in the Northwest (Zone Houillère) to the transition between blueschist and eclogite facies conditions in the Southeast (Internal Briançon-nais) is observed. A major discontinuity in metamorphic grade is located at the contact between Zone Houillère and Ruitor unit, as documented by a pressure gap of ~ 7 kbar. In general, the observed metamorphic field gradient is inverted and is interpreted to represent different depths of burial during subduction, which correlates with the paleogeographic position of the different units. basement rocks that underwent several metamorphic events. In such rocks, it is not always easy to relate metamorphic assemblages and events to the hercynian or alpine orogenesis. One of these areas is the Briançonnais domain of the Northwestern Alps. While in the southern part of the Western Alps, composed mainly of sediments, abundant evidence has been found for an Alpine high-pressure overprint (Goffé 1977;Goffé & Velde 1984), the alpine metamorphic evolution of the northern part, composed mainly of basement rocks, is still subject to debate.In this paper, we present a new metamorphic evolution for the whole area from a careful study of the petrology in the post-Hercynian metasediments occurring scarcely in the Briançonnais units along the trace of ECORS-CROP seismic line. These new PT-path data will provide new constrains for the geodynamic evolution of an area that plays a key role for the understanding of the evolution of the Western Alps.