Until relatively recently, we thought that the human central nervous system (CNS) was unable to regenerate. However, with the initial discovery of remyelination within the brain and the spinal cord in cat (Bunge, Bunge and Ris. Ultrastructural study of remyelination in an experimental lesion in adult cat spinal cord. J Biophys Biochem Cytol 1961;10:67–94.) and later in human (Prineas and Connell. Remyelination in multiple sclerosis. Ann Neurol 1979;5:22–31.), we know that regeneration can be quite extensive. This review will concentrate on CNS remyelination, indicating why it is important for various human neurodegenerative diseases including multiple sclerosis and spinal cord injury, and relate how stem cells may be involved—both in endogenous repair and in proposed therapies.