Transplantations for neurological disorders are limited by the supply of human fetal tissue. To generate larger numbers of cells of appropriate phenotype, we investigated whether human neural progenitors expanded in vitro could be modified with recombinant adenoviruses. Strong expression of beta-galactosidase was obtained in vitro. Two or three weeks after transplantation of engineered cells to the rat brain, we observed a small percentage of surviving neuroblasts strongly expressing beta-galactosidase in four out of 13 rats. Thus human precursor cells that have been genetically modified using adenoviruses are a promising tool for ex vivo gene therapy of neurodegenerative diseases.