In order to investigate the functional significance of possible adrenal amyloid infiltration in patients with renal amyloidosis, we performed corticotrophin stimulation tests in 15 patients having renal amyloidosis with no clinical evidence of adrenocortical insufficiency and 12 controls. In 7 of the patients, the cortisol increments obtained during the test were found to be consistent with primary adrenal insufficiency due to possible amyloid infiltration of the adrenal cortex; in contrast, in all control subjects, adrenal responses to the test were regarded as sufficient for proper adrenal function.