Two Spanish sibs with familial amyloidotic polyneuropathy (FAP) homozygous for the V30M-TTR gene, were diagnosed by DNA and protein analyses. Their clinical picture was very similar to the Majorcan FAP heterozygous patients except for the sensorimotor syndrome which was more aggressive. Noteworthy were clinical differences between the sibs concerning autonomic involvement, cranial neuropathy and kidney disturbances. These differences can be due to genetic and/or environmental factors.