Objective: To investigate the association between endometriosis and polymorphisms of N-acetyl transferase 2 (NAT2), glutathione S-transferase M1 (GSTM1), and cytochrome P450 (CYP) 1A1 genes in Korean infertile patients. Materials and Methods: A total of 303 infertile patients who had undertaken diagnostic laparoscopy during January, 2001 through December, 2003 at Samsung Cheil Hospital enrolled in this study. The patients were grouped according to laparoscopic findings: minimal to mild endometriosis (group I: n=147), moderate to severe endometriosis (group II: n=57), normal pelvic cavity (n=99). Peripheral blood was obtained and genomic DNA was extracted. The genotypes of each genes were analyzed using polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP). For NAT2, RFLP was used to detect the wild type (wt) and mutant (mt) alleles, enabling classification into slow (mt/mt) or fast (wt/wt or wt/mt) acetylation genotypes. For GSTM1, PCR was used to distinguish active (+/- or +/+) from null (-/-) genotypes. For CYP1A1, MspI digestion was used to detect the wild type (A1A1), heterozygote (A1A2) or mutant (A2A2) genotypes. Result: The genotype frequencies of NAT2 slow acetylator was 12.8%, 10.9%, 12.8% in group I, group II and control, respectively. The genotype frequencies of GSTM1 null mutation was 55.3%, 41.8%, 53.2% in group I, group II and control, respectively. The genotype frequencies of CYP1A1 MspI polymorphism was 16.3%, 9.1%, 18.1% in group I, group II and control, respectively. No significant difference was observed between endometriosis and normal controls in the genotype frequencies of the NAT2, GSTM1, CYP1A1 MspI polymorphism. Conclusion: The NAT2, GSTM1, CYP1A1 gene polymorphism may not be associated with the susceptibility of endometriosis in Korean women.