Angiogenesis is a fundamental component of normal development and pathologic processes within the eye. Complications due to abnormal ocular neovascularization remain the leading cause of visual loss throughout the world today. Neovascularization and the associated increase in vascular permeability are the underlying threats to vision in such diverse conditions as diabetic retinopathy, retinal vein occlusion, retinopathy of prematurity, exudative age-related macular degeneration, sickle cell retinopathy, radiation retinopathy, and numerous others. Although it has been appreciated for nearly one-half century that the clinical findings associated with ocular neovascularization suggest an etiology involving the elaboration of growth factors, the exact molecules involved and their mechanisms of action have remained incompletely understood. Recent developments in this rapidly evolving field have begun to elucidate the major factors responsible for modulating the neovascularization common to these conditions and have significant theoretic implications for the development of novel, nondestructive, pharmacologic treatment modalities.