PCR-RFLP was used to investigate the distribution differences of apolipoprotein E (APOE) alleles and genotypes between sporadic Alzheimer disease (AD) patients (n = 160) and healthy control individuals (n = 195) in Chinese Han population. The results showed that the allelic frequencies of APOE epsilon 2, epsilon 3 and epsilon 4 were 0.056, 0.713 and 0.231 in AD group respectively, and 0.082, 0.844 and 0.074 in control group respectively. The frequency of epsilon 4 allele was significantly higher in AD cases than in control subjects and epsilon 4 allele was associated with AD by an odds ratio (OR) of 3.82 (chi 2 = 28.70, P < 0.001). The probability for APOE epsilon 4-carriers to suffer from AD after 65 years old was 5.38 times of that for APOE epsilon 4 non-carriers (chi 2 = 29.76, P < 0.001), suggesting that age might affect the interaction between APOE epsilon 4 and AD. In addition, our results showed that the distributions of APOE alleles and genotypes were comparable among mild, moderate and severe dementia patients (P > 0.05), suggesting that APOE gene polymorphism was not likely to contribute to dementia severity of AD patients. The frequency of APOE epsilon 4 genotype in female patients was higher than that in male patients(43.0% vs. 36.5%) and females carrying APOE epsilon 4 allele had higher OR value than corresponding males (4.3 vs. 3.3), but the differences were not statistically significant (P > 0.05). As to epsilon 2 allele, its frequency was significantly lower in male subgroup than in female subgroup of AD patients and also than in male subgroup of normal control (P < 0.05), suggesting that epsilon 2 allele was possibly an AD protective factor in Chinese male population.