The role of the brain renin-angiotensin system in the ACTH response to ether stress in rats was investigated by injecting the angiotensin II receptor blocking drug saralasin, the angiotensin II converting enzyme inhibitors enalaprilat and captopril, and the renin inhibitor L 363714 intraventricularly and measuring the ACTH and corticosterone concentration in plasma 10 min after ether stress. ACTH and corticosterone were elevated to at least the same level in rats treated with the inhibitors as they were in rats treated with the corresponding vehicles; indeed, ACTH values were somewhat greater in stressed rats treated with the converting enzyme inhibitors and the renin inhibitor. ACTH values in the absence of ether were not affected by saralasin, enalaprilat, and captopril and were increased by L 363714. The data do not support the hypothesis that the brain renin-angiotensin system is involved in the maintenance of ACTH secretion or that it mediates the increase produced by ether stress.