Abstract : The Garonne Basin is the axial geomorphological entity of the Aquitain. In recent years, the middle valley of the Garonne River has been greatly revised. New sites and indications, particularly from the Lower and Middle Paleolithic, have thus been discovered and studied. The lithic industries yielded by these operations now provide us with robust reference bases, finally allowing comparisons of the behaviors of human groups during the Middle and Upper Pleistocene. It has been shown that the occupations were mostly multi-functional residential and are usually located as close as possible to the edges of terrace cuts. Geomorphologic and stratigraphic studies, along with the first dating elements and their correlations, allow the proposal of a first chrono-stratigraphic and chrono-cultural scheme, integrating the Midi Toulousain region in the general context of the occupation of Europe. It is possible that occupations of the Garonne valley by Acheulean groups did not become permanent until oxygen isotope stage 12. It has been shown that Upper Paleolithic and Late Middle Paleolithic occupations were almost totally absent, other than a few rare elements corresponding to temporary climatic warming periods. We thus deduct that environmental factors, which were harsh during glacial periods, rendered the Garonne valley particularly inhospitable, pushing prehistoric populations into the more protected areas surrounding the valley (karst). By projection, it is imaginable that the same phenomenon occurred during earlier glacial phases. The Garonne valley would therefore have alternately constituted a hub favoring circulation and a frontier limiting north/south contacts, depending on the succession of environmental conditions during the climatic fluctuations of the Pleistocene.