We report that prospectively isolated, human CNS stem cells grown as neurospheres (hCNS-SCns) survive, migrate, and express differentiation markers for neurons and oligodendrocytes after long-term engraftment in spinal cord-injured NOD- scid mice. hCNS-SCns engraftment was associated with locomotor recovery, an observation that was abolished by selective ablation of engrafted cells by diphtheria toxin. Remyelination by hCNS-SCns was found in both the spinal cord injury NOD- scid model and myelin-deficient shiverer mice. Moreover, electron microscopic evidence consistent with synapse formation between hCNS-SCns and mouse host neurons was observed. Glial fibrillary acidic protein-positive astrocytic differentiation was rare, and hCNS-SCns did not appear to contribute to the scar. These data suggest that hCNS-SCns may possess therapeutic potential for CNS injury and disease.