this study presents a review of published geological data, combined with original observations on the tectonics of the simplon massif and the Lepontine gneiss dome in the Western Alps. New observations concern the geometry of the Oligocene Vanzone back fold, formed under amphibolite facies conditions, and of its root between Domodossola and Locarno, which is cut at an acute angle by the Miocene, epi-to anchizonal, dextral centovalli strike-slip fault. the structures of the simplon massif result from collision over 50 Ma between two plate boundaries with a different geometry: the underthrusted European plate and the Adriatic indenter. Detailed mapping and analysis of a complex structural interference pattern, combined with observations on the metamorphic grade of the superimposed structures and radiometric data, allow a kinematic model to be developed for this zone of oblique continental collision. the following main Alpine tectonic phases and structures may be distinguished: pression, du soulèvement du dôme de gneiss du Lépontin et de l'abaissement de la dépression de la Dent blanche (Valpelline).Nous concluons que le poinçon adriatique s'est déplacé selon un chemin ré-gulier de direction NW à WNW, accompagné des déformations de raccourcissement NW-sE, W-E et sW-NE. studer