More than 1400 necropsies performed on patients with either a nontraumatic cerebral hemorrhage (400 cases) or with dementia over the age of 55 (1010 cases), or both, have been reviewed. There were 15 cases in which a cerebral hemorrhage had occurred together with cerebral amyloid angiopathy all of whom had been demented. Eight of the 15 patients were hypertensive. The 7 non-hypertensives showing only the amyloid change included two cases of "atypical" Alzheimer's disease with acute neurological features, and 5 cases of senile dementia (aged 72 to 78 years) coupled with focal neurological disorders. In the hypertensive patients, aged 67 to 86 years, with a progressive dementing syndrome and acute neurological signs, multiple ball-like hemorrhages (7 cases) and/or cerebral hematomas (3 cases) were associated with a combination of amyloid and hyalinar (hypertensive) angiopathy, often affecting segments of the same pial and cortical vessels. From these data and recent reports on lethal cerebral hemorrhage occurring spontaneously or after neurosurgical procedures in demented old people, cerebral amyloid angiopathy, which is not necessarily associated with systemic amyloidosis or severe (pre)senile cerebral degeneration, may be considered a rare but important cause of cerebral hemorrhage in the aged. The "vascular" type of presenile dementia, occasionally complicated by focal cerebrovascular lesions or bleeds, is considered a variant of Alzheimer's disease. The mechanism leading to formation of cerebral amyloid is unknown.