In endometriosis endometrial-like tissue is found most commonly in the peritoneal cavity, ovaries and rectovaginal septum. Endometriosis is characterised by a progesterone resistant endometrium and an immunologically compromised peritoneal microenvironment. The sequelae are infertility, dysmenorrhea, dyspareunia and chronic pelvic pain. Chronic pelvic pain causes disability and distress with a very high economic impact. The main treatment modality is surgery. Progestogens are effective in controlling the pain, and for treating recurrences. However, the mode of action on the target tissue is still uncertain, due to the progesterone resistance. The most likely mechanism of effect is on the inflammatory reaction surrounding endometriotic deposits. Other therapies include:- debulking by surgery, estrogen reduction by GnRH analogues and Danazol, inducing endomerial atrophy with the levonorgestrel releasing intra-uterine contraceptive, and gestrinone. Surgery is associated with a relatively high recurrence rate, The other medical treatments apart from progestogens are associated with a wide range of side effects. Progestogens are indicated for pain relief, bleeding and other symptoms of endometriosis when long-term medication or repeated courses of treatment are indicated. The main advantage of progestogen therapy is the relative lack of side effects. However, there is little data comparing different progestogens and progestogens have no effect on endometriosis related infertility.