Clinical, electromyographic and neuropathological studies were carried out at different stages of evolution of a familial amyloid neuropathy in 6 members of 3 families of French origin. The clinical onset was marked by sensory symptoms and signs in limb extremities, primary manifestations being alterations in pain and thermal sensitivity. This was followed by motor and amyotrophic disorders predominant in the lower limbs. Autonomic nervous system disorders were frequent later. Early electromyographic signs were diminished amplitude and increased duration of sensory potentials. Progression of the disease is shown by the onset of signs resulting from severe axonomyelinic lesions. Neuromuscular biopsy demonstrated the presence of amyloid deposits in the endoneurium in 5 of the 6 cases. Transmission appeared to be dominant autosomal. These cases pertain to group I of the amyloid neuropathies. The axonal lesions marking the onset of the affection could be secondary to biochemical alterations in prealbumin, responsible for amyloid formation. This hypothesis affords a basis for plasmapheresis which has been used in 3 patients.