BACKGROUND AND OBJECTIVES: Apolipoprotein A-I is the major lipoprotein constituent of high density lipoprotein in plasma. In this study, the role of two polymorphisms in the apo A-I gene was investigated on the serum lipid profiles and apo A-I levels in healthy men and women. SUBJECTS AND METHODS: Blood samples were obtained from 417 subjects (M : F=169 : 248, mean age 47.2 years). The apo A-I genotypes were determined by SNP-IT assays using the SNPstream 25KTM system. RESULTS: The frequencies of the A allele at the XmnI restriction site and position -75 bp were 0.25/0.23 and 0.19/0.17 in men and women, respectively. A strong positive linkage disequilibrium (D'=0.990) between two polymorphisms was detected. In men, the A allele at the XmnI restriction site was associated with significantly lower levels of triglyceride (p=0.028) compared to the G/G subjects, but no significant associations were detected between the G-75A polymorphism and any of the lipid traits examined. In women, each A allele for the XmnI restriction site and -75 bp polymorphisms were significantly associated with higher levels of apo A-I (p=0.032 and p=0.012). In the multiple regression analysis, the HDL, being a current drinker and the A allele of the XmnI restriction site polymorphism were major determinants of the serum apo A-I levels in women (R2=0.272, p<0.05). CONCLUSION: Our study showed that the A allele at XmnI restriction site in the apo A-I gene was associated with decreased triglyceride levels in men. Each A allele of two polymorphisms was associated with an elevated apo A-I level in women.