Familial amyloid polyneuropathy (FAP), a fatal disorder inherited in an autosomal dominant fashion, is characterized by systemic accumulation of polymerized transthyretin (TTR) in the peripheral nerves and systemic organs. Polyneuropathy is often a major manifestation of FAP. Although FAP was considered to be an endemic disorder, the advanced biochemical and molecular genetic analyses have shown worldwide occurrence. More than 100 different points of single or double mutations, or a deletion in the TTR gene, have been reported, and several different phenotypes of FAP have been documented, even for the same mutation in the TTR gene. Liver transplantation, which stops the production of amyloidogenic TTR in blood and replaces it with normal TTR, has been considered as an acceptable treatment for FAP. However, continuous amyloid deposition can occur from wild-type (normal) TTR in some patients. Currently, research an the inhibition of amyloid deposition by small organic molecules that are hypothesized to affect the fibril-forming ability of TTR is underway.