Endothelial cells are heterogeneous in structure and function. The endothelium transcends every organ, establishing a unique dialogue with the underlying tissue. Thus, the field of endothelial cell biology extends far beyond the traditional disciplines of cardiology, hematology and pulmonary medicine. The overall goal of this conference is to bring together scientists from diverse fields with a common interest in understanding the role of endothelial cell phenotypes in health and disease. The fields include vascular biology, hematology (hemostasis, endothelial precursor cells, circulating endothelial cells, sickle cell disease), oncology (tumor endothelium), pulmonary (pulmonary hypertension, acute lung injury), obstetrics (placenta), nephrology (hemolytic uremic syndrome), neurology (blood brain barrier), gastroenterology (liver circulation, veno-occlusive disease), dermatology (endothelial cell heterogeneity in skin), developmental biology, and non-linear dynamics/mathematics. At the present time, there is no venue for cross- disciplinary interactions between these various groups. The aims of this conference are to: 1) provide a forum for direct and intense discussion in a vital and emerging area, 2) discuss the mechanisms that mediate phenotypic heterogeneity of the endothelium, 3) apply these considerations to an understanding of vascular disease states, and 4) encourage new avenues of research and development.