Angiogenesis is the process by which new capillary blood vessels form from pre-existing ones. It is a complex multifaceted process that is essential for continued primary tumor growth, facilitation of metastasis, subsequent support for metastatic tumor growth, and cancer progression. Angiogenesis is regulated by both pro- and anti-angiogenic factors and is promoted during tumor development when an imbalance in these factors confers an “angiogenic switch” favoring a pro-angiogenic milieu. The regulators of angiogenesis include growth factors, proteases and protease inhibitors, cytokines and chemokines. As angiogenesis is a fundamental step in the transition of tumors from a benign state to a malignant one, the use of angiogenesis inhibitors has become a therapeutic strategy in the treatment of cancer.