The rat hippocampal formation was tested for the presence of factors that would accelerate neurite extension from chick parasympathetic (ciliary ganglion) or sympathetic (lumbar chain) neurons in vitro. Two growth factors were identified in extracts of this brain region. One accelerated neurite extension from sympathetic neurons and was blocked by antiserum to nerve growth factor. The other accelerated neurite extension from parasympathetic neurons but was not affected by the antiserum. These results suggest that specific growth factors account for the specificity of neuronal sprouting.