There is increasing evidence that certain components of the renin-angiotensin system (RAS) may have a crucial role in learning and memory processes. We have previously shown that brain-penetrating ACE inhibitors can reduce the incidence of Alzheimer diseases (AD) in elderly hypertensive patients and that hypertension treatment with brain penetrating ACE inhibitors slowed the rate of cognitive decline in mild-to-moderate AD patients with hypertension. We speculate that the favorable effects might be due to the direct effects of brain-penetrating ACE inhibitors on RAS in the brain, since no significant differences were found in the levels of blood pressure among the groups treated with several antihypertensive drugs. Brain penetrating ACE inhibitors might have benefits not only for the prevention but also for the treatment of mild to moderate AD with hypertension.