Basic fibroblast growth factor (bFGF) and nerve growth factor (NGF) were administered into the rat brain following unilateral fimbria-fornix transection. Both bFGF and NGF stimulated the sprouting of acetylcholinesterase (AChE) positive fibers in the hippocampus on the lesioned side. Furthermore, a small number of AChE-positive fibers were regenerated even when only the vehicle was administered. Rats treated with NGF as well as control group had only thin fibers, whereas those treated with bFGF had not only thin fibers but also thick fibers. These results indicate that intrinsic NGF is released and acts on damaged neurons directly, while bFGF acts them on directly and/or indirectly after brain injury.