Recombinant AAV-mediated gene delivery to the CNS can be performed either by direct delivery at the target site or from the periphery, using intramuscular injections and retrograde transport along motor neuron projections or intravenous injections and blood-brain barrier crossing.In this chapter, we describe: 1. Methods for recombinant virus administration, including stereotactic surgery, intramuscular, and intravenous administration. 2. Methods to evaluate the number and biodistribution of brain and spinal cord cells expressing the transgene by immunohistochemisty as well as the amount of transgene product by ELISA in the target region. 3. Methods to characterize the cellular specificity of transgene expression by double immunofluorescence. 4. Methods to quantify the amounts of viral DNA as well as of transgene mRNA by quantitative PCR and RT-PCR, respectively.