This chapter focuses on the existing need for stem cells, the advancement in techniques used to differentiate stem cells into specific neuron types, the results from transplantation in animal models, human clinical trials and the challenges yet to be overcome. Transplantation of these stem cells or their derivatives, and mobilization of already endogenous stem cells within the adult brain have both been proposed as future therapies for neurodegenerative diseases. Although brain stem and cortical areas may also be affected in Parkinson’s disease (PD), the neuronal population that is primarily affected is dopaminergic (DA) neurons of the substantia nigra, so transplantation of DA neurons is considered effective treatment for PD. Intrathecal transplantation of human motor neurons derived from neural Schwann cells in the spinal cord of the SOD1G93A mouse Amyotrophic Lateral Sclerosis model was reported to delay the onset of the disease and extend life span in these animals.