Ensheathing cells from fetal rat olfactory bulb were implanted into th e damaged adult rat brain to assess whether these cultured cells would survive in nonolfactory CNS areas and support the regrowth of nonolfactory axons. Cultures of primary ensheathing cells prelabeled with WGA-Au were embedded in a collagen matrix and implanted into a lesion cavity immediately following ablation of the fimbria-fornix in adult rats; the animals were sacrificed 4 weeks after surgery. Labeled ensheathing cells were observed only within the graft and not in the adjacent neural tissue. Immunostaining for p75 neurotrophin receptor revealed two characteristic morphologies of ensheathing cells within the graft; slender, spindle-shaped cells and larger, flattened cells. Although GFAP immunostaining revealed an intense glial reaction around the margin of the wound with host astrocytes sending cytoplasmic processes into the collagen matrices, no immunoreactive cells were found within the grafts. Histochemical detection of AChE revealed numerous reactive fibers confined to the regions of the grafts possessing ensheathing cells. Axons within the grafts were also immunoreactive for GAP-43. These initial experiments provide encouraging data concerning the survival of ensheathing cells for a minimum of 4 weeks following implantation into the adult rat brain and their ability to support the growth of new axons.