The past few years have been marked by substantial progress in preclinical studies of therapeutic gene transfer for neurologic disease using viral-based vectors. In this article, the authors review the data regarding (1) treatment of focal neuronal degeneration, exemplified by Parkinson disease, ischemia, and trauma models; (2) treatment of global neurologic dysfunction, exemplified by the mucopolysaccharidoses and other storage diseases; (3) peripheral nervous system diseases including motor neuron disease and sensory neuropathies; and (4) the use of vectors expressing neurotransmitters to modulate functional neural activity in the treatment of pain. The results suggest that a number of different viral vectors may be appropriate for gene transfer to the central nervous system for specific disease processes, and that for the peripheral nervous system herpes simplex virus-based vectors appear to have special utility. The results of the first human gene therapy trials for neurologic disease, which are just now beginning, will be crucial in defining the next step in the development of this therapy.