Broad enthusiasm has recently developed for the potential use of iPS cells as a source of new oligodendrocytes for myelin repair. Induced pluripotential stem cells are pluripotential cells that have been generated by the reprogramming of somatic cells to a less phenotypically committed stem cell ground state, through the concurrent forced expression of a small set of transcription factors critical to maintenance of the self-renewing stem cell phenotype.61- 62 Most typically, iPS cells have been generated from dermal fibroblasts, cotransduced with a number of stem cell–associated transcription factors, including POU5F1(OCT3/4), SOX2, MYC, KLF4, and/or NANOG.63- 64 Induced pluripotential stem cells are pluripotential, as defined by their ability to generate cells of all major germ layers and teratomas in vivo. Induced pluripotential stem cells were first generated from mouse65 and human66- 67 fibroblasts and have since been generated from a variety of cell types and differentiated into an even broader variety of committed progenitor cells and somatic phenotypes. Most notably among these, the production of dopaminergic neurons from iPS cells validated their ability to generate postmitotic neuronal derivatives.68 Induced pluripotential stem cells have the decided advantage over hES cells of being readily derived from adult somatic cells, such as dermal fibroblasts or marrow stromal cells. Once so derived, they may be used to produce cell types of interest that may be transplanted as autologous grafts back to the very patients from whom they were generated, thereby obviating the need for posttransplant immune modulation. Yet, to date, no terminally differentiated myelinogenic oligodendrocytes have yet been reported from human iPS cells. Once this important milestone is reached, we may begin to explore the potential for generating populations of iPS-derived oligodendrocytes for autologous grafting in the myelin disorders. That being said, the hurdles that will need to be overcome are similar to those facing hES-derived GPCs and oligodendrocytes: GPCs derived from iPS cells share the same risks as those derived from hES cells, in terms of both unintended differentiation of unrestricted contaminants, as well as frank tumorigenesis. Just as with the use of GPCs derived from hES cells, those generated from iPS cells will need to be purified before use, so as to minimize the risk of any potentially tumorigenic contaminants accompanying the transplanted cell populations. That being said, this risk should be obviated by the many fluorescence- and magnetic-activated cell sorting techniques now available for enriching neural and GPCs to clinically appropriate purity.1- 2 As a result of these considerations, future studies will need to consider the stringent selection for committed GPCs before any attempt at hES or iPS cell-based therapy.