The administration of a dehydrating agent like glycerol may improve the audiometric thresholds and decrease the summating potential in the electrocochleographic recordings of some Méière's diseases. There are many discussions concerning the endolymphatic sac's rôle in this cases. To clarify this subject we have reviewed the labyrinth's liquids physiopathology, the structural observations in cases of Ménière's diseases, the animals models date. We conclude that the presence of an endolymphatic sac is not necessary for obtaining a positive glycerol test. The clinical meaning of this test is discussed.