Background : Endometriosis is defined as the presence of endometrial tissue outside the uterus, causing diverse diseases, including infertility, pelvic pain, dysmenorrhea, and constipation. While there is a growing body of evidence that genetic and immunologic factors play important roles in the pathogenesis of the disease, HLA-A, B antigens have been reported to be associated with the risk of endometriosis in the Japanese population. This study was performed to determine whether the susceptibility to advanced endometriosis is also associated with HLA-A, B antigens in the Korean population, which is the closest ethnic group to Japanese. Methods : We recruited 50 Korean patients with advanced endometriosis confirmed by surgical and histolological examinations. Distribution of HLA-A and B antigens was compared with that of 200 unrelated ethnically matched individuals. HLA-A and B genotyping was carried out using a PCR-sequence specific oligonucleotide hybridization method. Results : An increased frequency of B39 was observed in endometriosis patients compared with control subjects, but the difference was not statistically significant after correcting for multiple comparisons (4.0% patients vs 0.8% controls, OR=5.5, 95% CI=1.21-25.04, P=0.03, Pc=not significant). No significant differences were found between the patients with endometriosis and the general control group with regards to the distribution of other HLA-A and B antigens. Conclusions : The findings of the present study suggest that the susceptibility to advanced endometriosis, unlike in the Japanese population, is not associated with HLA-A, B antigens in the Korean population.