Nitric oxide is an important factor to regulate the biochemical reactions in the body such as expansion of blood vessel, neural conduction and antimicrobial activity. There are two forms of nitric oxide synthase and iNOS has attracted most attention because it is involved in the development of diabetes and cardiac disease condition. There are several regulatory sequences in the promoter region of iNOS gene. One of them is (CCTTT)n. It has been reported that the number of tandem repeat of (CCTTT)n varies from population to population. So, we analyzed (CCTTT)n polymorphism in Korean genome for the purpose of comparison. According to our present study Koreans are different from other Asians reported previously because $(CCTTT)_{10}$ is the highest incidence as opposed to $(CCTTT)_{12}$ for other countries. This study should facilitate the understanding of the expression of iNOS gene in different population.