We investigated the immunohistochemical alterations of angiotensin converting enzyme (ACE), angiotensin II and ATI receptor in the parietal cortex in Alzheimer's dementia (AD) to reveal the contributive role of the brain renin-angiotensin system in the disease process. In controls. ACE, angiotensin II and ATI immunoreactivities were localized to pyramidal neurons of the cortex. The staining intensity was distinctly increased in AD for all three antigens, involving predominantly cortical layer V, which may reflect the enhanced brain renin-angiotensin system activity in the disease process. In addition, a prominent perivascular ACE and angiotensin II immunoreactivity surrounding some cortical vessels in aged controls and AD patients points to an underlying microvascular pathology in the process of neurodegeneration, (C) 2001 Elsevier Science Inc. All rights reserved.