Fourteen years after transplantation into the striatum of an individual with Parkinson's disease, grafted nigral neurons were found to have Lewy body–like inclusions that stained positively for α-synuclein and ubiquitin and to have reduced immunostaining for dopamine transporter. These pathological changes suggest that Parkinson's disease is an ongoing process that can affect grafted cells in the striatum in a manner similar to host dopamine neurons in the substantia nigra. These findings have implications for cell-based therapies and for understanding the cause of Parkinson's disease.