A method for inducing a partial dysfunction of the endolymphatic sac and its effect was investigated. Acetazolamide as well as amiloride caused collapse of the lateral intercellular spaces in the endolymphatic sac epithelium and a subsequent mild endolymphatic hydrops. These changes indicate a decreased absorption rate of endolymph in the endolymphatic sac. Colchicine caused a disturbed secretory activity of the sac induced by glycerol. Animals treated with colchicine showed marked signs of inner ear malfunction after additional treatment with glycerol, which might indicate that the secretory activity in the sac is closely related to the regulation of inner ear fluid homeostasis and functional disturbance.