A clinicopathological study was made on 65 patients from a small area of Nagano Prefecture, Japan, with hereditary generalized amyloidosis with polyneuropathy to clarify the clinical variety of the disease. Forty-five patients from Ogawa village showed similar clinical features. The age of onset ranged widely from 16 to 62 years. The main neurological manifestations were polyneuropathy starting in the legs and autonomic dysfunction. Lower cranial nerves were also affected in the advanced stages. Severe cardiac and renal involvement was uncommon. All these clinical features are consistent with type I familial amyloid polyneuropathy (FAP). The remaining 20 patients from five unrelated kinships showed unique clinical pictures. Two families from Ogawa village had type I FAP, but 4 out of the 5 affected patients showed marked nephropathy with heavy proteinuria from an early stage. Of the three other families, one, with 10 patients, was notable for the involvement of the central nervous system. Most of the patients showed cerebellar ataxia and pyramidal tract signs in addition to a sensorimotor and autonomic peripheral neuropathy. Another family had 2 siblings who had severe amyloid heart disease from the onset and developed polyneuropathy with autonomic features at an advanced stage. In the third family, onset occurred in the sixth decade in all 3 patients and the course was mild in 2, although the clinical features were those of typical type I FAP. Immunohistochemical study revealed that the amyloid fibril proteins in the patients with all four unusual clinical phenotypes were related to plasma prealbumin. The most common form of hereditary generalized amyloidosis in Japan is type I FAP, but the disease shows considerable variety in the age of onset and involves more systemic organs than previously recognized. The newly recognized clinical forms of hereditary generalized amyloidosis with severe amyloid heart disease or central nervous dysfunction indicate clinical heterogeneity of hereditary amyloidosis with polyneuropathy.