Northwestern France is characterized by the presence of many Middle Palaeolithic sites, covering the entire period. The Saalian phase is less documented, partly for taphonomic reasons. The lithic industries indicate mastery of all production systems for flakes, blades, points and to a lesser extent, bifaces. During the Upper Pleistocene, occupation of this territory by Neandertal groups is important. The vast majority of these lithic series cannot be attributed to cultural facies of Mousterian defined by Bordes, due to the low number of retouched tools. Aside from some typical Mousterian of Acheulean tradition bifaces and blade production characteristic of the Early Weichselian, which are stylistic and cultural markers, there is nothing to differentiate Mousterian groups. In an attempt to identify their cultural identities, lithic assemblages were apprehended globally, using the operative sequence concept from the acquisition of raw material to the final objectives of the different production systems, and abandonment of tools. The situation is considered from each chronostratigraphic phase to try to distinguish the settlement patterns of this region. This renewed approach to technical studies points to a wide diversity of Neandertal adaptive faculties, which can be interpreted in terms of cultural diversity