Diseases of glia, including astrocytes and oligodendrocytes, are among the most prevalent and disabling, yet least appreciated, conditions in neurology. In recent years, it has become clear that besides the overtly glial disorders of oligodendrocyte loss and myelin failure, such as the leukodystrophies and inflammatory demyelinations, a number of neurodegenerative and psychiatric disorders may also be causally linked to glial dysfunction and derive from astrocytic as well as oligodendrocytic pathology. The relative contribution of glial dysfunction to many of these disorders may be so great as to allow their treatment by the delivery of allogeneic glial progenitor cells, the precursors to both astroglia and myelin-producing oligodendrocytes. Given the development of new methods for producing and isolating these cells from pluripotent stem cells, both the myelin disorders and appropriate glial-based neurodegenerative conditions may now be compelling targets for cell-based therapy. As such, glial cell-based therapies may offer potential benefit to a broader range of diseases than ever before contemplated, including disorders such as Huntington's disease and the motor neuron degeneration of amyotrophic lateral sclerosis, which have traditionally been considered neuronal in nature.