Drugs currently used for anti-angiogenic therapy which are based on monoclonal antibodies to VEGF and its receptors are of limited efficiency. Endoglin (CD105) is a protein receptor of TGF-beta superfamily involved in ligand binding and transduction of signals regulating VEGF-independent mechanisms of angiogenesis. CD 105 is highly expressed on membranes of endothelial cells of vessels in growing tumors. It plays a crucial role in determination the state of activation or quiescence of endotheliocytes. CD 105 is present also on membranes of tumor stromal cells (macrophages, fibroblasts, pericytes). High density of CD105-positive microvessels in tumors corresponds with its aggressivness, spreading to regional lymph nodes and poor prognosis. In patients with progressing tumors soluble form of endoglin in peripheral blood may be detected. Monoclonal antibodies to CD 105 and their derivatives are regarded as a basis for creation of new generation of anti-angiogenic reagents for visualization of tumor vessels, for direct effect on endothelium or for targeted drugs delivery to growing tumors.