The goal of this thesis was to characterise temperature sensitive immortalised mesencephalic progenitors (CSM14.1-cells) in vitro and in vivo after transplantation into the striatum of adult Hemiparkinsonian rats. In vitro the time dependent expression of cell type specific markers for neural stem cells, dopaminergic (DAergic) progenitors and mature (DAergic) neurons under defined differentiation conditions in culture (1% FCS, 39° C) was investigated for 14 days. In this in vitro system CSM14.1-cells underwent a similar DAergic differentiation as it occurs during embryonic development in rodents. Three months after transplantation it was demonstrated that the PKH26-labelled CSM14.1-cells were viable, migrated about 300-400 µm and were mainly colocalized with GFAP. A DAergic differentiation was not observed and therefore a DAergic reinnervation of the adult striatum did not occur. Apomorphine-induced rotations in these animals did not differ significantly from those of sham-transplanted controls.