The 250-km-long deep seismic survey across the Pyrenees from the Aquitaine basin to the Ebro basin was sponsored by French and Spanish organizations, and was carried out in 1985 and 1986. This first seismic survey of an entire orogenic belt crosses the deformed boundary between the Iberian and European plates, the geometry of which has been greatly debated during a recent past. The main results are summarized as follows: (1) The entire crust shows well-defined reflectors with a general fan shape geometry. (2) The Iberian crust seems to be thicker than the European one. Both are limited by a well-defined deep layered material above the Moho discontinuity. (3) Only the Iberian crust was significantly thickened by a southward overstacking of slabs. (4) Near the surface in the external domains, reflectors define accurately the geometry of major thrusts and structures affecting the Mesozoic and Cenozoic cover of the Pyrenees. Using ECORS data (Etude Continentale et Océanique par Réflexion et Réfraction Sismique), the structure of the studied section of the belt can be modeled considering the nature and continuity of reflectors beneath the surface trace of the North Pyrenean fault considered as the initial vertical boundary between Iberian and European plates.