Pendred syndrome is an autosomal recessive disorder characterized by sensorineural hearing loss, goiter, and a partial defect in iodide organification, and is the most common syndromic hearing loss. Hearing loss is congenital in most cases and is accompanied by an enlarged vestibular aqueduct and a Mondini cochlea. Pendred syndrome and autosomal recessive deafness-4 (DFNB4) with enlarged vestibular aqueduct comprise a phenotypic spectrum caused by mutations in SLC26A4. Recently, mutations in FOXI1 and KCNJ10 have also been identified in DFNB4. Molecular mechanism of hearing loss and goiter remains to be elucidated, and therapies which can reverse or prevent the progression of the symptoms are not available. Here, we describe advances in the basic, clinical, and translational studies on Pendred syndrome.