Amyloidosis is a multisystem disease which may cause organ loss. Renal involvement is the most common clinical problem in amyloidosis, however involvement of endocrin organs is possible. In this study to assess adrenocortical function and to evaluate the usefulness of low dose ACTH test in patients with renal amyloidosis, we determined cortisol, 17-hydroxyprogesteron (17-OHP) and 11-deoxycortisol (11-DOC) responses to both 1 microg and 250 microg Synacthen. We also determined the size of adrenal glands radiologically by using computerized tomography. Twenty one patients with renal amyloidosis and 16 healthy subjects for hormonal evaluation, and 20 patients with renal amyloidosis and 22 healthy subjects for radiologic evaluation were included in the study. In four patients (19%) peak serum cortisol levels following stimulation with the low dose of Synacthen were less than 20 microg/dL (550 nmol/L). Two of them had also subnormal cortisol response to the 250 microg Synacthen stimulation test. Basal and stimulated levels of 11-DOC were lower than those of control values (p=0.000 and p<0.01 respectively). The mean 11-DOC responses to stimulation with 1 microg Synacthen were also significantly lower than the values obtained after the simulation with 250 microg Synacthen (p<0.01 and p=0.000). Cortisol responses to the stimulation with 250 microg Synacthen were also lower than the control responses (p<0.05). 17-OHP responses were similar to the control values in both tests. In the radiological evaluation the mean maximum width of right adrenal glands and the mean anterior and maximum width of left adrenal glands were significantly greater in the patient group (p<0.01). In conclusion, adrenal involvement and adrenal insufficiency is common in amyloidosis. Low 11-DOC levels in amyloidosis is a new finding and further detailed studies is required to explain its cause.