Recent advances in gene transfer methods, especially development of a high titer recombinant adeno-associated viral (AAV) vector, are making gene therapy for Parkinson's disease (PD) a feasible therapeutic option in the clinical arena. Efficient and long-term expression of genes for dopamine (DA)-synthesizing enzymes in the striatum restored local DA production and allowed behavioral recovery in animal models of PD. Moreover, sustained expression of a glial cell line-derived neurotrophic factor gene in the striatum rescued nigral neurons and led to functional recovery in a rat model of PD, even when treatment was delayed until after the onset of progressive degeneration. A clinical trial to evaluate the efficacy of subthalamic transduction to produce inhibitory transmitters is underway.