To evaluate the influence of the apolipoprotein E (ApoE) epsilon4 allele on the age at which Alzheimer-like lesions appear in the brain, we analyzed the degree of cerebral beta-amyloidosis and neurofibrillary tangle formation in the hippocampal formation and adjacent cortical areas 28, 27, and 36 of persons who had died between the ages of 50 and 93 years and who had shown no signs of clinical dementia. The occurrence of the three common polymorphisms of the ApoE gene in this sample of 147 routine autopsy cases from eastern Germany was comparable to previously reported values in European and North American populations: ApoEepsilon2/2, 0.7%; ApoEepsilon2/3, 14.3%; ApoEepsilon2/4, 4.1%; ApoEepsilon3/3, 56.5%; ApoEepsilon3/4, 22.4%; and ApoEepsilon4/4, 2.0%. Nondemented persons carrying the ApoEepsilon4 allele were significantly more likely to have senile plaques, diffuse amyloid deposits, cerebrovascular amyloid, and neurofibrillary tangles than were those lacking E4. Comparing the two largest ApoE subgroups, ApoEepsilon3/3 and ApoEepsilon3/4, the relative increase in the occurrence of beta-amyloid in the epsilon3/4 group was evident by the mid-60s, with the relative increase in neurofibrillary tangles in this group emerging slightly earlier. The ApoEepsilon2 allele appears to delay the appearance of the lesions somewhat. We conclude that ApoEepsilon4 promotes the early appearance of beta-amyloid and neurofibrillary tangles in the elderly and that the increased frequency of these lesions is related to the higher risk of Alzheimer disease in persons bearing the ApoEepsilon4 allele.