The damp environment and density of animal population in Camargue are good arguments for the study of leptospirosis. A serological and epidemiological survey on 642 blood samples revealed 36 (5.6%) with significant antibody titers. Icterohaemorrhagiae is followed by Canicola, Grippotyphosa, Australis and Ballum... The most endemic area is not Camargue but the area situated at the northeast (Basse-Durance). Women are twice more affected than men. These two results are not consistent with our initial hypothesis. It is always advisable to seek the etiology of fevers of unknown origin.