The ability to deliver specific genes to individual cells within an intact animal or human offers enormous possibilities, both for scientific analysis of the gene's function and for therapeutic intervention in genetic diseases. The application of in vivo gene delivery to the nervous system has lagged behind that of other systems because of its complexity and because retroviral vectors used in other tissues do not infect non-dividing cells such as terminally differential neurons. This book considers the approaches developed to overcome these difficulties allowing the in vivo delivery of specific genes in a safe and efficient manner. The first section of the book covers these alternatives: adenovirus, adeno-associated virus, and herpes simplex virus. The second half of the book covers retroviral vectors to deliver genes to dividing neuronal precursor cells and to specifically target dividing cancer cells in the brain, as well as to engineer non-neuronal cells in culture subsequent to transplant into the brain. The final section deals with the non-viral mediated means, which include transgenic animals and direct injection of plasmid DNA and anti-sense oligonucleotides into the brain.