After several decades of pre-clinical development, cell- and gene-based therapies for Parkinson’s disease (PD) are now actively being explored. In this special supplement to the Journal of Parkinson’s Disease, “Repairing the Parkinsonian Brain,” experts highlight some of the current strategies being pursued to restore lost function and replace what is lost in the PD brain, with special emphasis on the challenges associated with translating advanced therapeutic approaches into pioneering clinical trials.