Several antiangiogenic agents, including bevacizumab, sunitinib, and sorafenib, which mainly target the VEGF signaling system, have been approved for the treatment of human cancers. These drugs have been paired with conventional chemotherapeutic agents to treat different types of cancers, including colorectal and lung cancers; however, the patient response rate and resultant increase in overall survival time have been rather modest. The current antiangiogenic regimen is far from optimal. Improvements of therapeutic efficacy and minimization of adverse effects and drug resistance are urgent tasks that are most likely to be resolved by understanding the molecular mechanisms underlying tumor angiogenesis. The aim of this article is to discuss these clinically related issues, to highlight several recent examples of the complex interplays between tumor-produced angiogenic factors, and to propose a new paradigm for improvement of therapeutic intervention of tumor angiogenesis.