Jacques Maas is gynaecologist and subspecialist in reproductive medicine. He is a member of the expertise center endometriosis of the department Obstetrics and Gynecology, Maastricht University Medical Center. Other aspects of his clinical work are endoscopic surgery, benign gynecology, psychosomatics and sexual medicine. He is ambassador of the World Endometriosis Society and founder and past-president of the dutch SIG Endometriosis. He was a working group member of the recently published ESHRE guideline Endometriosis. Topics of interest in endometriosis research are mainly related to patient centeredness. He is main applicant of the SOMA trial: Surgical or Medical treatment of Endometrioma.