The renin-angiotensin system(RAS) genes have been extensively studied as etiologic essential hypertension( EH) candidate genes in human populations worldwide. The angiotensin I-converting enzyme(ACE) plays a key role in the RAS for the regulation of blood pressure. Recent studies on the association of ACE gene polymorphisms with EH and the related cardiovascular diseases presented conflicting results. Therefore, we investigated the association of three polymorphisms(I/D, G14480C and A22982G) in the ACE gene with EH in Koreans. We studied a sample population of 699 Koreans, comprising of 471 controls and 228 cases with EH, which were recruited from Cardiovascular Genome Center in Korea. The ACE gene polymorphisms were determined by polymerase chain reaction and SNP-IT assay. The allele frequency of G14480C polymorphism showed significant difference between normotensives and hypertensives in female group(P=0.0353). After adjustment for age and BMI, logistic regression analysis indicated that the odds ratio(OR) of the ACE I carriers(II+ID) for a risk of EH over the DD genotype was 1.698(95% CI, 1.006-2.864, P=0.0458), and OR for the comparison of 14480 GG subjects versus GC and CC subjects combined was for EH 1.787(95% CI, 1.076-2.967, P=0.0236) in females. In haplotype analysis, major three haplotypes(ICA, IGG, and DGG) were significantly associated with EH in study populations. We conclude that ACE polymorphisms appeared to have apparent association with EH in Koreans, who have a more homogeneous genetic structure than any other ethnic groups.