The comparison of the foraminifera of the salt-works of Salin de Giraud with those from the littoral of the Gulf of Beauduc has shown that the microfaunas from these environments differ in the following respects: - In the salt-works there are 2 foraminiferal associations: one of restricted aspect (Galabert), the other exhibiting distinct marine influences (Vaisseau/Vieux-Rhône). Both associations however are characterized by dwarfed, little ornamented and often deformed individuals, and both have low indices of diversity not exceding 4, suggesting restricted environmental conditions. Further, the microdistribution in the salt-works is heterogenous which seems to be linked to the sedimentary environment (sandy bottom, mud, algal mats, etc.). - In the littoral area, where the index of diversity may go up to 8, there occur numerous foraminiferal species which are not found living in the restricted environments of the salt-works. Dead tests may be transported a) from the sea into the salt-works; b) within the different areas of the Salin, or c) from the salt-works to the sea. The hypothesis that the foraminiferal populations within the salt-works is being each year introduced from the sea by the pumping-in of sea water into the compartiments of the Salin, has been rejected. In fact, the populations of the restricted environment of the Salin de Giraud are firmly established and of permanent nature. They are, naturally, subjected to large variations in temperature and salinity. The upper limit of their tolerance to salinity lies in the vicinity of 50 to 80 g/l (doubtfully up to 150 g/l) NaCl.