BACKGROUND: Studies have indicated that the more certain etiological factors of vascular dementia are the sites, size and number of cerebrovascular lesions, but there are arguments all the time in the relationship of genetic factors, especially apolipoprotein E gene, with the occurrence and development of vascular dementia. OBJECTIVE: To analyze the relationship between the polymorphism of apolipoprotein E gene and vascular dementia in stroke patients. DESIGN: A non-randomized grouped comparative observation at the same time. SETTING: The Laboratory of Neurology, the Second Affiliated Hospital of Chongqing University of Medical Sciences.PARTICIPANTS: Totally 121 inpatients with stroke were selected from the Department of Neurology, the Second Affiliated Hospital of Chongqing University of Medical Sciences from January 2000 to December 2001. All the patients were accorded with the diagnostic standards for cerebrovascular diseases set by the Second National Academic Meeting for Cerebrovascular Disease, and confirmed by cranial CT or MRI. According to with vascular dementia or not, they were divided into vascular dementia group (n =58) and non-vascular dementia group (n =63). In the vascular dementia group, there were 37 males and 21 females, the average age was (59±8) years. They were all in accordance with the standard of the third edition of Diagnostic and Statistical Manual of Mental Disorders (DMS-Ⅲ), without conscious disturbance and language disorder; hospitalized within 3 days after the attack of cerebrovascular disease. In the non-vascular dementia group, there were 37 males and 26 females, the average age was (59±9.5) years. They all had no intellectual disturbance within 3 months after the attack of cerebrovascular disease. All the subjects agreed to supply blood samples for the experiment. METHODS: ①Fasting venous blood (2 mL) was drawn from each patient in the ming to extract DNA. The frequencies of apolipoprotein E genotypes and alleles were detected with polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). ② Gene frequency was calculated using the gene calculation, genotype or allele frequency were compared using the Chi-square test. MAIN OUTCOME MEASURES: The frequencies of apolipoprotein E genotypes and alleles were compared between the two groups. RESULTS: All the 121 patients were involved in the analysis of results. Five genotypes of apolipoprotein E gene were detected, and ε2/2 genotype was not detected. The frequency of ε3/3 was the highest in both groups, the frequencies of ε4/4 genotype and ε4 allele were obviously higher in the vascular dementia group [9%(5/58), 24.1%] than in the non-vascular dementia group [3% (2/58), 19.0%, P＜ 0.05]. The genotype frequencies of ε2/2,ε2/4, ε3/3, ε2/3 and ε3/4 and the allele frequencies of ε2 and ε3in the vascular dementia group [0, 2%(1/58), 57%(33/58), 3%(2/58), 29%(17/58); 2.6%, 73.3%] were not obviously different from those in the non-vascular dementia group [0, 2%(1/58), 59%(37/63), 6%(4/63), 30%(19/63); 4.0%, 77.0%, P＞ 0.05]. CONCLUSION: The ε4/4 genotype of apolipoprotein E gene is closely correlated with the occurrence of vascular dementia, the ε4 allele may be a genetic susceptible factor of vascular dementia.