Cell replacement remains a viable option for Parkinson's disease. In the past few years, we and others have succeeded in producing large numbers of dopamine neurons from human embryonic stem cells, a continual source of somatic cells. However, the poor survival and function of the in vitro-generated dopamine neurons following transplantation into the brain becomes a roadblock to stem cell therapy. The proposed study is to identify optimal conditions, including the combination with growth factor-producing glial cells before and after transplantation, for improving the survival, maintaining the dopaminergic identity, and promoting subsequent functional integration of the dopamine neurons following transplantion into Parkinsonian rats. Our long-term goal is to translate this technology to Primate Parkinson's models and eventually Parkinson's patients.