Six patients with advanced Parkinson's disease have been grafted with human fetal neuronal cells. This clinical work is based on the technique originally described by the groups of Lund, Sweden and Créteil, France, with which we closely collaborate. A first group of 3 patients was grafted between 1995 and 1996, with neuronal tissue obtained from same-day abortions. We have observed bilateral improvement of motor functions after unilateral transplantation into the putamen. One patient had a second graft, into the heterolateral putamen, one year after the first one. Another group of 3 patients was operated between 1997 and 1998, and received grafts of hibernated tissue, in order to facilitate the technical organization of the transplantation procedure. Altogether, these clinical results are encouraging, but the technical and ethical limitations related with the use of human fetal tissue prompted us to develop alternative solutions, such as the use of xenografts and the transplantation of genetically modified cells.