Endometriosis is a complex gynaecological disorder that affects nearly 1 in 7 women of reproductive age. Ectopic dissemination of endometrial cell and their subsequent implantation are the mechanisms involved in the development of endometriosis. Endometriosis is a common multifactorial disease caused by an interaction between multiple gene loci and environment. Causes of stress on immune functioning or may be genetically determined. Environmental factors can be responsible for immunosuppressive activities in patient with endometriosis. In addition, toxin modulates steroid receptors expression resulting in altered tissue specific responses to hormones. Chronic immunosuppression in combination with hormonal regulation may have facilitated the aberrant growth of endometrial tissue within the peritoneum. However, the mechanism appears to require endometrium and retrograde menstruation in most cases of the disease.