['To investigate the involvement of inflammation in the development of endometriosis.', 'Case-control study to investigate the association between endometriosis and four inflammation-related genes: interleukin (IL)-6, IL-10, IL-1 beta, and cyclooxygenase-2.', 'University hospital.', 'We had 196 cases with pathologically proved endometriosis and 397 disease-free women as control subjects.', 'A total of 12 single nucleotide polymorphisms (SNPs) were selected for genotyping, including functional SNPs and common tagging SNPs.', 'Logistic regression and haplotype analyses were performed to evaluate the genetic effect with adjustment for other covariates.', 'Genotypes at each SNP were in Hardy-Weinberg equilibrium in either case or control subjects, except for rs1800871 at IL-10 in the case subjects (P=.04). We found that the individuals carrying minor allele C of a functional promoter SNP rs1800871 at IL-10 was associated with a reduced risk by approximately twofold compared with the common TT genotype. The T allele was reported to have a lower gene expression level than the C allele, suggesting inadequate suppression of inflammation leading to endometriosis development. Haplotype analysis of the IL-10 gene did not yield a better result. Other genes were not associated with endometriosis.'] Does a functional promoter polymorphism in interleukin-10 gene influence susceptibility to endometriosis?