Abstract: Objective To assess the influences of cholesterol 7-alpha hydroxylasel(CYP7A1) gene polymorphism on hyperlipidemia in middle-aged and old populations.Methods We recruited 451 individuals(men and women) aged 45 to 75 years in a population-based cross-sectional survey in Nanjing city,and randomly divided them into dyslipidemia group(N=223) and control group(N=228).Medical examinations,including total cholesterol(TC),triglyceride(TG),high density lipoprotein cholesterol(HDL-C),and low density lipoprotein cholesterol(LDL-C)),and CYP7A1 gene polymorphism,were carried out among the participants.Results The frequency of alleles A and C in CYP7A1 204 in dyslipidemia group and normal control group was 30%,70%,and 30.7%,69.3%,respectively.The allele frequency and genotype frequency distributions were consistent with Hardy-Weinberg balance law(P＞0.05).Individuals in dyslipidemia group with AA,AC,CC genotypes showed significant differences in TC(P＜0.05),while HDL-C and LDL-C levels of the individuals with A genotype were significantly reduced than those with AC,CC genotypes(P＜0.05).The TC levels were significantly different between the individuals with CC and AC genotype in the control group(P＜0.05).Conclusion The middle-aged and old populations with the CYP7A1 gene mutant may have an increased risk of dyslipidemia.