 This is a randomized, double-blind and placebo controlled trial using individualised homeopathic medicine dynamized estrogen to treat chronic pelvic pain of endometriosis. Patients with endometriosis, chronic pelvic pain and a set of signs and symptoms similar to those of the estrogen adverse events will be recruited in the Sector of Endometriosis of the Clinical Division of Gynaecological of the Hospital das Clínicas of the Faculty of Medicine of the University of Sao Paulo. The selection process was carried out through the analysis of medical charts and self-completing of structured questionnaires. Satisfied the inclusion criteria, fifty patients were randomly and distributed to receive dynamized estrogen or placebo. The primary clinical outcome is the severity of the chronic pelvic pain. Statistical analysis will be by intention-to-treat and per protocol comparing homeopathic drug with placebo after 24 weeks of intervention. 