The fate of neonatal glia (mostly glial fibrillary acidic protein-positive astrocytes), cultured on nitrocellulose papers and implanted into cortical lesion cavities, was examined in adult mice and rats. In mice, a Y-chromosome-specific probe and in situ hybridization techniques were used to identify male cells. Male-female grafts allowed visualization of donor glia and their behaviour after transplantation; female-male grafts allowed an analysis of how host cells responded to the presence of the implants. There was substantial intermixing of cells, with many donor glia migrating away from the implants and host cells migrating onto both sides of the nitrocellulose paper. In rats, donor glia were labelled with fluorescein-conjugated latex microspheres prior to transplantation on nitrocellulose polymers. The rat data were broadly consistent with those obtained from the mouse; moreover, immunohistochemical studies in rats suggested that the majority of host cells migrating onto the previously cell-coated papers were astrocytes. In a number of studies, glia-coated polymers have been used in an attempt to promote the regrowth of axons across lesion sites in the brain and spinal cord. The present work suggests that both transplanted and host glia may influence the regenerative growth seen in such implants.