Glial cells are thought to play an important role in the regulation of neural pattern formation, e.g. by guiding migrating neuroblasts and growth cones to their target regions. In addition to these supportive roles, astro- and oligodendroglia have also been attributed inhibitory functions. Thus, these lineages are believed to constrain the pathways of migrating neurons and growth cones. Recent studies have led to the current view that the inhibitory roles of the glia of the central nervous system (CNS) may be important for neural pattern formation. Furthermore, inhibitory effects of glia may play an essential role in the failure of CNS regeneration, e.g. in the astrocytic scar. Advances have been made in deciphering the molecular basis of glia-mediated inhibitory influences in the CNS. The present review focuses on the tenascin gene family of extracellular matrix glycoproteins. Of these, tenascin-C and -R are expressed in developing and lesioned neural tissue and embody both stimulatory and anti-adhesive or inhibitory properties for axon growth.