Dissociated chick neocortical neurons were cultured on cryostat sections of the rat central nervous system. The neurons adhered to and grew on the gray matter of the tissue derived from various parts of the central nervous system (CNS), but were not seen on the white matter. However, cell attachment was seen on sciatic nerve. This preferred adhesion to and growth on the gray matter of the CNS was abolished by irradiation of ultraviolet light which is supposed to denaturate proteins without disturbing tissue architecture. These observations suggest that differential cell adhesion to the gray and white matter could be ascribable to localization of some adhesive molecule(s) in the gray matter or to localization of nonpermissive molecule(s) in the CNS gray matter.