Preclinical neuroscience has advanced rapidly over the past two decades. New approaches for treating neurological disease, including gene-based therapies, nervous-system growth factors, stem cells, novel vaccines, and modulation of the immune system, offer the potential to prevent cell loss and degeneration in the brain, rather than attempting to compensate for loss after it has occurred. I will review one of these prospective therapies: growth-factor gene therapy for Alzheimer's disease, an approach that is currently the subject of a phase I clinical trial. Other disease targets for gene therapy will also be discussed, including Parkinson's disease, Huntington's disease, inborn errors of metabolism, and cancer. The progress of gene-therapy clinical trials is aiding the transition to molecular and gene-targeted therapeutic approaches which have the potential to improve dramatically the prognosis of neurological disease.