Although neurogenesis is observed in the human adult brain, its regulation and role are unknown. Among lots of factors promoting neurogenesis, we focused on fibroblast growth factor-2 (FGF-2), because it is known to be an important factor for neural stem cell culture. In our study, neurogenesis was upregulated in the dentate gyrus (DG) following cerebral ischemia and kainic acid-induced seizure in wild type animals, but it was reduced in FGF-2-/- mice. When FGF-2 was overexpressed using gene transfer technique with herpes virus vector, neurogenesis was upregulated, and, furthermore, degenerative changes of the hippocampus after traumatic brain injury were also reduced. These results suggested that FGF-2 is a critical factor to regulate neurogenesis in the DG after brain injury. Administration of growth factors after brain injury may provide a strategy for repair of the brain following neuronal injury and other CNS disorders.