Retinal neovascularization (NV) is a major cause of the blindness associated with such ischemic retinal disorders as diabetic retinopathy, retinopathy of prematurity and retinal occlusion. Neovascularization is induced by complex interactions among growth factors and cytokines. Some studies confirm that VEGF play a central role in neovascularization, there remain some questions as to why VEGF antagonists are only partially effective. Transforming growth factor-beta (TGF-beta) has been implicated in the development of neovascularization (Gerard et al. 2000). Smad 4 plays the most important role in the TGF-beta signal transduction (Zimowska 2006). In this study, we used the model of oxygen-induced retinopathy in neonatal mice to investigate the expression of TGF-beta1 and Smad 4 mRNA in the retina, to explore their role in the development of retinal neovascularization.