Although the activity of the renin-angiotensin system is known to decrease with age, the antihypertensive efficacy of angiotensin-converting enzyme (ACE) inhibitors has been demonstrated in the elderly. To examine the role of the renin-angiotensin system in hypertension in the elderly, we evaluated the antihypertensive response to enalapril and to TCV-116, an angiotensin II type-1 receptor antagonist, in elderly patients with essential hypertension. A single oral dose of enalapril (10 mg) increased plasma renin activity (PRA) and reduced the angiotensin II concentration, whereas a single oral dose of TCV-116 (4 mg) increased both PRA and the angiotensin II concentration. Blood pressure was significantly reduced by these drugs from 4 h after administration. Basal levels of PRA and angiotensin II declined with age. However, the changes in blood pressure produced by either TCV-116 or enalapril did not correlate with age. These results suggest that the activity of the renin-angiotensin system in plasma declines with age, and that the extrarenal renin-angiotensin system may play a role in hypertension in the elderly.