6-10% of women of childbearing age suffer from endometriosis, which is mainly manifested by dysmenorrhea, non-menstrual pelvic pain and dyspareunia. Several treatment strategies, including surgical ones, are proposed but they are sometimes insufficient because endometriosis-related pain is frequently accompanied by sensitization. Endometriosis surgery, when indicated, is therefore changeably effective, even though the lesions have been completely resected. Patients therefore consult Pain Units seeking for the effective treatment as the pain persist even after surgical management of endometriosis. Vagus nerve stimulation is a non-invasive technique that includes an anti-inflammatory effect and a modulation of neurotransmitter production (adrenaline, norepinephrine; serotonin, acetylcholine). Yuan and Silberstein published a general review on the technique. Migraine and depression are one of the selected indications. In addition, Napadow et al. published favourable results in a short series of patients with chronic pelvic pain. The Investigators of this study have treated some patients with this technique with a result deemed satisfactory which leads to propose a randomized study to confirm this impression.