A 53-year-old man with nonfamilial prealbumin-type amyloid polyneuropathy had severe motor, sensory, and autonomic polyneuropathy, beginning at age 48 years. These clinical features closely resembled familial amyloid polyneuropathy (FAP), but abnormal serum prealbumin levels, specific to FAP (Japanese type), were not detected by radioimmunoassay; DNA sequence for prealbumin was normal. Thus, the diagnosis of FAP was excluded. A possible diagnosis of systemic senile amyloidosis was also considered.