Objective:To explore the distribution of the (CA) n dinucleotide repeats polymorphism of the endothelial nitric oxide synthase (eNOS) gene in Chinese han nationality.Methods:(CA) n repeats polymorphism of the endothelial nitric oxide synthase (eNOS) gene from 291 Chinese healthy subjects were analyzed by polymerase chain reaction(PCR)-denature polyacrylamide gel electrophoresis (PAGE)-silver stain.Results:Ninety-three genotypes and twenty-three different alleles were identified in 291 Chinese healthy subjects.The distribution of genotypes was in accordance with the Hardy-Weinberg equilibrium( P >0.05).The size of PCR fragments ranged from 144 to 188bp containing 19～41 CA repeats and the frequency of (CA)n ranged from 0.34%～14.1%.The heterozygosity(H) and polymorphism information content(PIC) were 0.85 and 0.83 respectively.Significant differences were found in frequencies of eleven alleles including 22-repeats

23-repeats

26-repeats

27-repeats

28-repeats

30-repeats

31-repeats

32-repeats

33-repeats

34-repeats and 35-repeats between Chinese and Caucasians.Conclusion:This site is referred to as a genetic marker with high polymorphism information content.And the distribution of this genetic marker is different in different ethnic groups.