The clinical motor dysfunction in Parkinson s disease (PD) is primarily linked to the depletion of dopamine in the striatum consecutive to the loss of the large dopaminergic neurons in the substantia nigra. Despite intense investigations, no effective therapy is available to prevent the onset, or to halt the progression of the neuronal cell loss. Here, we hypothesize that autologous adult neural stem cells (NSCs) are an attractive source for cell therapy to treat PD. They overcome the ethical issues inherent to the use of human fetal tissue or embryonic stem cells. NSCs derived from adult tissue also open the possibility for autologous transplantation, where NSCs are taken out from the patient, expanded and differentiated in vitro and re-implanted back as dopaminergic precursor cells.