This study explored the effects of the lipid-soluble free radical scavenger, alpha tocopherol (vitamin E), on neuronal injury and glial protein accumulation in a well-characterized, three-dimensional, mixed neuronal and glial culture system derived from fetal rat prosencephalon. As these reaggregated spheroidal cultures grew and enlarged, they developed small central areas of necrosis (presumably due to nutritional compromise) which we used as a model for central nervous system injury. Treatment with vitamin E (delivered in egg phosphatidylcholine liposomes beginning on day 8 in vitro) did not alter the appearance of the central necrotic areas, but it strongly suppressed the reaction of adjacent astroglia and microglia. Histological examination showed that by day 35 in vitro control cultures which received liposomes without tocopherol were nearly devoid of neurons and contained many glial and microglial cells. In contrast, tocopherol-treated cultures contained many viable-appearing neurons and did not exhibit an overgrowth of glia. Both glial fibrillary acidic protein (as measured by immunoassay) and lipid peroxidation (as estimated by malondialdehyde levels) were markedly reduced in the tocopherol-treated cultures. We speculate that the vitamin exerts its protective effect on injured nervous tissues by scavenging free radicals, stabilizing cellular membranes, and quenching the cascade of biochemical events that follows necrosis in brain. This work suggests that the signal(s) to initiate gliosis are mediated, at least indirectly, by free radical formation.