Endometriosis is a common gynecological condition, responsible for significant morbidity and social-economic impact. Although the condition has been recognized for many years, the underlying pathophysiology is poorly understood. In turn, this results in inadequate treatment and high recurrence rates. Various theories try to explain the presence of endometrial tissue outside the uterine cavity. However, none of them can explain all disease locations and appearances, and it is unclear how these fragments establish into endometriotic lesions. New vessel formation has long been recognized as a feature of endometriosis, often clearly visible at laparoscopy. Recent work has focused on identifying the role of vascularization in the pathogenesis of endometriosis, by allowing lesions to establish and grow. In this review the authors outline the basic mechanisms of angiogenesis and vasculogenesis in the human eutopic endometrium, and consider how this data can be applied to endometriotic implants. Furthermore, the authors discuss molecular mechanisms of angiogenesis and vasculogenesis, and how this may be used to therapeutic advantage in the treatment of endometriosis.