Endometriosis, a gynecologic pathology, is defined by the presence of a tissue similar to uterine endometrium, which is located in places other than physiologically appropriate. These endometrial heterotopic islets contain glands and stroma and are functionally capable of responding to exogenous, endogenous, or local hormonal stimuli. Endometriosis affects 8%-10% of women of reproductive age; in 30% of the women, the condition is associated with primary or secondary infertility. In several instances, endometriosis persists as a minimal or mild disease, or it can resolve on its own. Other cases of endometriosis show severe symptomatology that ends when menopause occurs. Endometriosis can, however, reactivate in several postmenopausal women when iatrogenic or endogenous hormones are present. Endometriosis is occasionally accompanied by malignant ovarian tumors, especially endometrioid and clear cell carcinomas. Its pathogenesis is widely debated, and its variable morphology appears to represent a continuum of individual presentations and progressions. Endometriosis has no pathognomonic signs or symptoms; it is therefore difficult to diagnose. Because of its enigmatic etiopathogenesis, there is currently no satisfactory therapy for all patients with endometriosis. Treatments include medications, surgery, or combined therapies; currently, the only procedures that seem to cure endometriosis are hysterectomy and bilateral salpingo-oophorectomy. In this paper, we review the most controversial and enigmatic aspects of this disease.