We have demonstrated an association between apolipoprotein E (apoE) gene polymorphisms and Alzheimer’s disease (AD) in 163 Japanese patients by means of PCR. We found a significant increase in risk of nonfamilial AD for apoE allele ε4 in these individuals; this trend decreases with the increase in onset age. In centenarians, the distribution of apoE gene alleles is similar to that in the general population. The protective effect of allele ε2 against the development of AD is not statistically significant in our analysis. This indicates that apoE polymorphism is associated with AD regardless of race and that the age of onset is related to the apoE gene in the development of A