Following the successful progress of gene therapies in treating rare disease, they are now beginning to be applied to CNS disorders, including Parkinson's and Alzheimer's disease, and other serious conditions. Drug delivery to the brain has long been a challenge, and a great deal of research is being focused on identifying various strategies that are able to ferry medicines across the blood-brain barrier (BBB), which typically blocks the transport of molecules and particles into the brain, and effectively deliver their therapeutic payloads. In this two-part feature, the progress being made in the field will be explored.