This book presents an overview of the diagnostic performance of non- or semi-invasive tests for endometriosis in peripheral blood, endometrium, saliva, peritoneal fluid and urine. The value of existing and emerging systems biology technologies for biomarker development is addressed in several chapters on genetics, microarrays, proteomics and metabolomics. Although tests with high sensitivity and acceptable specificity have been developed, sometimes validated in independent populations and seem promising, more research is needed to translate these data into clinical benefit for patients and coordinate efforts internationally to standarize analysis, reports and operating procedures. The gold standard to diagnose endometriosis is currently through laparoscopic inspection with histological confirmation, a surgical procedure with rare but significant potential risks for the patients.