Parkinson's disease is a complex disorder characterized by degeneration of dopaminergic neurons in the substantia nigra in the brain. Stem cell transplantation is aimed at replacing dopaminergic neurons because the most successful drug therapies affect these neurons and their synaptic targets. We show here that neural progenitors can be grown from the olfactory organ of humans, including those with Parkinson's disease. These neural progenitors proliferated and generated dopaminergic cells in vitro. They also generated dopaminergic cells when transplanted into the brain and reduced the behavioral asymmetry induced by ablation of the dopaminergic neurons in the rat model of Parkinson's disease. Our results indicate that Parkinson's patients could provide their own source of neuronal progenitors for cell transplantation therapies and for direct investigation of the biology and treatments of Parkinson's disease. Disclosure of potential conflicts of interest is found at the end of this article.