Abstract: Objective To study the polymorphism of +252 site in intron 1 of tumor necrosis factor (TNF)-β gene in relation to genetic susceptibility of endometriosis. Methods Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was employed to detect the polymorphism of +252 site in intron 1 of TNF-β gene in 82 Chinese Han patients with endometriosis in Guangdong Province and 80 Han patients without endometriosis (control group), and the relation between TNF gene polymorphism and the risk of endometriosis was analyzed. Results The +252 site of TNF-β allele and genotype distribution showed significant difference between endometriosis and control groups (χ2=6.562, P<0.05; χ2=6.562, P<0.05), and relative risk of endometriosis in relation to allele A was increased by 1.793 fold. The risk of endometriosis was 3.33-fold higher in women of AA genotype than those of GG genotype (χ2=6.562, P<0.05). Conclusions Allele A in TNF-β gene +252 site can significantly increase the relative risk of endometriosis in women in Guangdong, among which TNF-β AA genotype might be one of the genetic susceptible factors for endometriosis.