The angiotensin converting enzyme (ACE) is a key component of the renin-angiotensin system thought to be important in the pathogenesis of hypertension and cardiovascular diseases. Deletion polymorphism in the ACE gene may be a risk factor for myocardial infarction. The insertion/deletion (I/D) polymorphism of the ACE detected by PCR analysis appears to be associated with hypertension in Koreans and its nucleotide was subcloned into T-vector and its nucleotide sequences were determined. We also examined an association between hypertension and genetic variance of ACE. We identified the angiotensin I-converting enzyme genotype in 127 hypertensive and 189 normotensive Korean subjects. The distribution of ACE genotype II, ID, DD were 39.2%, 40.2%, 20.6% respectively and the frequency for ACE alleles I and D were 0.593 and 0.407, respectively in all subjects. The frequency of D allele in Korean males is higher than that of Korean females (male; 0.438 : female; 0.267), and the frequency of I allele in Korean females is higher than that of Korean males (female; 0.733 : male; 0.562). Genotype distributions of angiotensin I-converting enzyme genes in Korean normal adult population were different from that of Caucasians (P<0.001). There were no significant differences in genotype frequency between the hypertensive control group (n=127) and the normotensive group (n=189). We observed significant differences of ACE genotype distribution between the male group and the female group in total (P=0.001) and in hypertensive Korean subjects (P=0.013).