ABSTRACT Endometriosis is a debilitating disease involving the growth of endometrial glands and stroma outside the uterus. The primary symptoms are pelvic pain and infertility. Nearly half of affected women have chronic pelvic pain, and in 70% of those, the pain occurs during menstruation. Pain with sex (“dyspareunia”) and infertility occur in close to half of women affected by endometriosis. Less common symptoms include urinary or bowel symptoms. About 25% of women have no symptoms. Endometriosis can have both social and psychological effects. Currently, definitive diagnosis is achieved by surgical biopsy. Because of the invasive nature of this method, the diagnosis and treatment of endometriosis is considerably delayed, with average time from symptom onset to diagnosis being 10 years. The consequence of this significant delay is prolonged and progressive pain, a risk of infertility and considerable social/economic impact. The purpose of this study is to develop non-invasive screening methods for the early detection of endometriosis. Specifically, we will target DNA methylation signatures carried by circulating fragments of extracellular DNA, referred to herein as cell-free DNA (cfDNA). These fragments, which are detected in a variety of fluid reservoirs including blood plasma, convey epigenomic information both about their cell type of origin and its pathological state. Our over-arching hypothesis is that altered DNA methylation signatures in the uterine tissue of endometriosis patients are detectable via analysis of plasma-derived cfDNA. In this study we will build a foundation of preliminary data towards the development of methods for the early non-invasive detection of endometriosis.