The fundamental reagent capability and clinical significance of ApoE gene typing has been investigated. The result of each test shows that the reagent capability satisfied the expected standard. Four-hundred thirty-nine samples classified into three groups (Alzheimer's disease (AD), other types of dementia and nondementia) were measured to examine the clinical significance. The rate of epsilon 4 genotype of each group was 31.5%, 14.6%, 10.4%, respectively. The AD group had a higher rate than the other groups (p < 0.001). The measurement of ApoE genotype is suggested to be useful as one of the guidelines in the diagnosis of AD.