Bevacizumab (Avastin), a vascular endothelial growth factor antagonist, is the first approved antiangiogenic drug for the treatment of human cancers. Endostatin, a broad-spectrum endogenous angiogenesis inhibitor, has recently been approved in China for cancer therapy. Today, hundreds of antiangiogenic molecules targeting different signaling pathways are being tested for their anticancer efficacies at preclinical and clinical stages. The underlying mechanisms by which these antiangiogenic cancer drugs used in combination with chemotherapy confer survival advantages for cancer patients are not fully understood. Thus, deeper understanding the mechanisms of tumor angiogenesis and actions of these therapeutic molecules is crucial for designing more potent anticancer drugs.