Objectives: To investigate the distribution and functional significance of $CYP11{alpha}$ $(tttta)_n$ microsatellite polymorphism in Korean patients with polycystic ovary syndrome Materials and Methods: Analysis of $CYP11{alpha}$ $(tttta)_n$ microsatellite polymorphism was carried out on DNA samples from 97 patients with polycystic ovary syndrome and 70 normal controls. Comparison were done between PCOS patients and controls concerning $CYP11{alpha}$ $(tttta)_n$ microsatellite polymorphism genotype or allele frequencies. Results: The most frequent allele observed in the controls was an allele with six repeats (60.7%). Significant difference in the frequency of genotype (4R (-) genotype) having no copy of four-repeatallele were observed between PCOS patients and controls (66.0% vs 34.0%, p=0.038, OR=1.939). But no significant difference was observed in the serum levels of total testosterone or free testosterone between 4R (+) genotype and 4R (-) genotype among PCOS patients. However, hyperandrogenic PCOS patients with 4R (+) genotype showed a higher serum testosterone levels compared to controls (mean $pm$ S.D: $0.49{pm}0.21;ng/ml$ vs $0.37{pm}0.18;ng/ml$, p=0.037). Conclusion: The alleleic distribution of $CYP11{alpha}$ $(tttta)_n$ microsatellite polymorphism in Korean subjects were different from those reported in Caucasians. $CYP11{alpha}$ $(tttta)_n$ microsatellite polymorphism was associated with polycystic ovary syndrome in the Korean population, and may play a role in the synthesis of androgens in patients with polycystic ovary syndrome.