As part of a community-based study of Alzheimer's Disease (AD) in a Nigerian population aged 65 years and over, we have determined apolipoprotein E (APOE) genotypes on 56 subjects (39 controls and 17 subjects with dementia, including 12 with AD). The epsilon 4 allele of APOE was not associated with AD or dementia in this community-based sample. The epsilon 4 allele frequency was 17.6% in demented patients and 16.7% in AD patients compared with 20.5% in the control subjects. These findings are in marked contrast to the strong association between the epsilon 4 allele and AD in our previously reported study with African Americans.