Angiogenesis, an jee oh JEHN uh sihs, is the formation and growth of new blood vessels in the body. Angiogenesis plays an important role in the growth of tissues and the repair of tissues from wounds or infection. Abnormal angiogenesis, however, occurs in a variety of diseases. Excessive angiogenesis occurs in cancer and an eye condition called macular degeneration. Insufficient angiogenesis can occur following stroke.