Introduction Pendred's syndrome is a recessive autosomal disease, traditionally defined as the association of deaf-mutism, goiter and dysfunctional iodide organization revealed by the perchlorate discharge test. It represents 4 to 10% of the causes of congenital hypoacusis. Although described more than a 100 years ago, the association of thyroid and cochleo-vestibular damage remained unclear for many years. Genetic abnormalities Progress in molecular biology has revealed that the disease is related to alterations in the PDS gene situated on chromosome 7. The PDS gene is responsible for the production of pendrine, protein involved in anion (l-, Cl-) transportation, notably in the apical pole of the thyreocyte and the cochlear duct, where the endolympha is produced. Practical implications The truncation of pendrine related to the genetic alterations be responsible for the morpho-functional alterations in the cochlear apparatus and the thyroid. In this perspective, Pendred's syndrome would appear as a genetic disorder in anion transportation.