Progestins are synthetic compounds that mimic the effects of progesteron. For over 50 years, oral progestins have been demonstrated to be effective in the treatment of endometriosis. They were reported to reduce or eliminate pain symptoms in approximately 90% of the patients. Progestins are available in many forms, including oral preparations, injections, subdermal implants and intrauterine systems. Continuous progestin use is an effective therapy for the treatment of painful symptoms associated with endometriosis but there had been no evidence of progestin use being superior to other types of treatment in endometriosis-related pain symptoms.