Grafting cells to the CNS is a useful approach to address fundamental and clinical issues in neurobiology. Recently, a hybrid technique - the genetic modification of cells followed by intracerebral implantation - has emerged, which may potentially enhance the power of CNS grafting. However, several methodological considerations need to be addressed to test the reliability of this new approach. Progress in the gene transfer-grafting technique has implications for expanding the range of issues and problems that may be addressed in both the basic science and clinical arenas.