This chapter is intended to provide an overview of stem cells and its therapeutic applications in neurology. Stem cells are unique type of cells with ability to divide indefinitely in culture and produce many types of new cells. Cells similar to ESCs exist in adult tissue. The most primitive stem cell for tissue or organ is the best stem cell to use. Stem cell therapy has emerged as a promising novel therapeutic endeavor for traumatic brain injury, SCI, stroke, and neurodegenerative diseases among others in experimental studies. Great strides have been made in the isolation, purification and directed differentiation of stem cells. The best option would be to obtain autologous marrow derived cells (stimulated by GCSF), mobilized (by GCSF) peripheral blood derived cells, and those derived from human umbilical cord blood or amniotic fluid. Such sources are free from ethical issues and host rejection. Current research is aimed at finding the appropriate source of stem cells for a given indication, ways of expanding and perpetuating these cells in culture, best route of administration of these cells (intracisternal, intraventicular, intrastriatal and intravenous or intra-arterial), and methods to overcome rejection.