Previous work has shown that transplanted dissociated glial cells derived from neonatal rats can myelinate areas of the myelin deficient (md) rat spinal cord. In the present studies we have examined the ability of adult glial cells, either as suspension of mixed glial cells or as 01 positive oligodendrocytes purified by cell sorting, to myelinate md rat axons following transplantation. Mixed glial cell preparations from adult rats myelinated large areas of either, dorsal, lateral or ventral columns. These areas contained clumped, transplanted oligodendrocytes. In addition, preparations containing over 90% 01 positive oligodendrocytes were also capable of myelinating large numbers of axons upon transplantation. These results suggest that adult oligodendrocytes may play an important role in remyelination of the adult CNS.