In order to evaluate the involvement of the peripheral autonomic nervous system in the pathogenesis of type 1 familial amyloid polyneuropathy, the urinary excretion rates of catecholamines and serum dopamine-beta-hydroxylase (DB/) activity were examined in 22 patients at various clinical stages. Changes in both indices were closely linked to the progression of the illness; urinary excretion rates of catecholamines were first decreased in patients suffering from moderate autonomic dysfunction, while serum DBH activity was significantly reduced only in patients with far advanced disease. These findings suggested that patients with advanced disease might be suffering from a chronic deficiency of catecholamines in the peripheral sympathetic nerves. Administration of L-dopa, however, failed to improve the clinical manifestations.