Transforming growth factor beta (TGF-B) family members are multi-functional cytokines that play a key role in cellular growth, proliferation, and differentiation. The aim of the study was to investigate whether the TGF-B1-509 gene polymorphism could be used as a marker of susceptibility in endometriosis. Women were divided into two groups: endometriosis (n = 150) and non-endometriosis (n = 159). Polymorphisms for TGF-B1-509 genes were amplified by polymerase chain reaction and detected after restriction enzyme digestion. Genotypes and allelic frequencies in both groups were compared. Genotype proportions and allele frequencies of TGF-B1 gene polymorphisms differed significantly in both groups. Proportions of C homozygote, heterozygote, and T homozygote for TGF-B1 gene polymorphisms were 9.3/61.3/29.4% in the endometriosis group and 41.3/58.5/0% in the non-endometriosis group. Alleles C and T for TGF-B1 gene polymorphism were 40/60% (endometriosis) and 70.8/29.2% (non-endometriosis). Association of endometriosis with TGF-B1-509 gene polymorphism exists. T homozygote and T allele for TGF-B1 are associated with higher susceptibility to endometriosis.