The aim of the present study was to develop a model culture system for the study of factors controlling regeneration of axons from injured adult mammalian central nervous system. We show, for the first that retinal ganglion cells (RGC) dissociated from adult rat retina, regrow processes in vitro over long distances under over appropriate conditions in monolayer culture. Most importantly, adult RGC depend completely upon the presence of a preformed layer of neonatal cortical astrocytes, whereas RGC from neonatal retinae are supported by indigenous retinal glia which spread and proliferate to form a monolayer of cells upon which RGC regrow processes. Adult retinal glia fail to spread on the culture surface and proliferate in the same way and we suggest that this is a major factor in limiting the survival of adult RGC on an acellular substrate such as polylysine. Laminin does not substitute for the presence of a glial monolayer. These findings indicate that at least one type of adult CNS neuron is capable of regenerating its processes in vitro in an environment which includes a cellular component of CNS tissue.