Human embryonic stem (hES) cells proliferate and maintain their pluripotency for over a year in vitro (M. Amit, M. K. Carpenter, M. S. Inokuma, C. P. Chiu, C. P., Harris, M. A. Waknitz, J. Itskovitz-Eldor, and J. A. Thomson. 2000. Dev. Biol. 227: 271-278) and may therefore provide a cell source for cell therapies. hES cells were maintained for over 6 months in vitro (over 100 population doublings) before their ability to differentiate into the neural lineage was evaluated. Differentiation was induced by the formation of embryoid bodies that were subsequently plated onto appropriate substrates in defined medium containing mitogens. These populations contained cells that showed positive immunoreactivity to nestin, polysialylated neural cell adhesion molecule (PS-NCAM) and A2B5. After further maturation, these cells expressed additional neuron-specific antigens (such as MAP-2, synaptophysin, and various neurotransmitters). Calcium imaging demonstrated that these cells responded to neurotransmitter application. Electrophysiological analyses showed that cell membranes contained voltage-dependent channels and that action potentials were triggered by current injection. PS-NCAM and A2B5 immunoselection or culture conditions could be used to produce enriched populations (60-90%) which could be further differentiated into mature neurons. The properties of the hES-derived progenitors and neurons were found to be similar to those of cells derived from primary tissue. These data indicate that hES cells could provide a cell source for the neural progenitor cells and mature neurons for therapeutic and toxicological uses.