In the early sixties, remyelination was first observed in animal models of demyelination and described a few years later in multiple sclerosis. The spontaneous remyelination process is now well documented. Remyelination by transplantation of myelin-forming cells has been attempted. Transplanted Schwann cells can myelinate a central nervous system lesion but the remyelination is limited to the area of implantation. Oligodendrocytes or precursor cells are much more invasive and have been shown to migrate from the implantation site to the lesion at a distance of several millimeters. Thus, remyelination by transplantation of myelin-forming cells is possible at least in animal models, the oligodendrocytes being more efficient.