We studied the frequency, severity, and clinical correlations of cerebral amyloid angiopathy (CAA) in 117 CERAD subjects with autopsy-confirmed AD. Eighty-three percent showed at least a mild degree of amyloid angiopathy. Thirty of 117 brains (25.6%) showed moderate to severe CAA affecting the cerebral vessels in one or more cortical regions. These brains also showed a significantly higher frequency of hemorrhages or ischemic lesions than those of subjects with little or no amyloid angiopathy (43.3% versus 23.0%; odds ratio 2.6, 95% CI = 1.1 to 6.2). High CAA scores also correlated with the presence of cerebral arteriosclerosis and with older age at onset of dementia. Our findings suggest that factors contributing to non-AD-related vascular pathology (e.g., atherosclerosis) may play a role in amyloid deposition in cerebral vessels in AD.