Summary: Recently, the most significant studies in the field of angiogenesis are related to trials concerning the evaluation of the prognostic significance of endothelial markers. By using an estimation of the expression of endothelial cell markers, immunohistochemical studies can assess for the continuity of the vascular intima, as well as allow for the distinction of early, late and mature forms of endothelial cells. The determination of the endothelial cell phenotype using markers such as CD34, CD31, CD133, e-NOS and von Willebrand factor may provide a valuable tool for the monitoring of both normal physiology as well as neoplastic diseases.