The ability to transplant an unlimited supply of clonally related neural progenitors that, in the brain, have the capacity to differentiate into neurons and glia in an anatomically and, perhaps, functionally appropriate manner, may not only facilitate developmental inquiries, but may also circumvent the limitations of primary fetal tissue for neural transplantation. These types of transplants also make possible new strategies for gene therapy and repair of the CNS, including replacement of degenerated cells, engineering donor cells to be resistant to toxins, delivery of missing metabolic or other gene products, over-expression of molecules, and substitution of alternate metabolic pathways.