The purpose of this chapter is to analyze existing data on the interactions of angiogenic growth factors in vivo and in vitro. It is shown that many growth factors act synergistically to elicit more potent angiogenic responses in endothelial cells. At the same time, some factors antagonize each other. Possible mechanisms of these phenomena are discussed. Anti-angiogenic strategies for cancer and retinopathies accounting for growth factor interactions are delineated with emphasis on combination therapy and targeting master regulators, such as HIF-1α and protein kinase CK2.