We have characterized the cellular localization of stem cell factor (SCF) and c‐kit receptor (c‐kitR) in the adult mouse nervous system in situ and in culture by using immunocytochemistry. We found that SCF is largely confined to the neuronal population in normal brain, whereas c‐kitR is expressed by glial cells as well as some neurons. We also found that astroglia at an early stage of culture (7 days in vitro) are strongly SCF positive and weakly c‐kitR positive. Microglia in cultures express both SCF and c‐kitR, but the immunostaining of SCF is weak and diffuse when microglia are cultured in the presence of colony stimulating factor‐1. Northern blot analysis confirmed the expression of mRNAs of c‐kit and SCF in cultured neurons, astroglia, and microglia. The addition of recombinant SCF to astroglia in culture upregulates the expression of mRNAs of nerve growth factor, brain derived neurotrophic factor, and ciliary neurotrophic factor. These observations suggest that SCF/c‐kitR signaling is involved in neuron‐neuron as well as neuron‐glia interactions. J. Neurosci. Res. 47:1–15, 1997. © 1997 Wiley‐Liss, Inc.