We report two families in whom the index cases satisfied the classical diagnostic criteria of Pendred's syndrome. In family I, two siblings were deaf, and one was normal. In family II, both parents and two offspring were deaf. Computed tomography scans performed in five of six of these deaf individuals showed enlarged vestibular aqueducts in all cases, and Mondini cochlea only in family II. Affected members in family I were compound heterozygotes inheriting the paternal allele with a novel mutation S398del in exon 10 and a maternal allele with two mutations IVS13+9C-->G in intron 13, in addition to H723R. In family II, the mother and one child carried both the novel intronic IVS8-2A-->G and H723R mutations, whereas the father and index case were homozygous for the IVS8-2A-->G mutation. A perchlorate discharge test was positive in 50% of cases tested. In conclusion, we concur that radiological and molecular studies should be performed for confirmation of Pendred's syndrome. We report, for the first time, a Pendred's syndrome family in which affected members had three mutations, as well as a second family in whom the intermarriage of two Pendred's syndrome patients resulted in Pendred's syndrome offspring.