A study demonstrates that mammalian neural stem (NS) cells can be cultured in defined conditions without requiring a specialized niche. NS cells derived from mouse embryonic stem (ES) cells, as well as human ES cells and fetal brain, can be maintained in culture using fibroblast growth factor 2 (FGF-2) and epidermal growth factor (EGF). These cells undergo symmetrical self-renewal and retain the ability to differentiate into neurons and astrocytes. NS cells express markers of radial glia, developmental precursors of neurons and glia, and can be propagated in adherent cultures. They are capable of generating neurons upon growth factor withdrawal and maintain diploid chromosome content. NS cells derived from fetal brain and neurospheres can be expanded in culture and differentiate into neurons and astrocytes. When transplanted into the adult brain, NS cells integrate and differentiate into neurons and astrocytes. NS cells do not give rise to teratomas, unlike ES cells. They are capable of long-term survival and differentiation in both fetal and adult brain environments. NS cells can be cryopreserved and genetically modified, offering potential for genetic intervention in the nervous system. The study highlights the importance of EGF and FGF-2 in NS cell self-renewal and differentiation, and suggests that NS cells may be closely related to a radial glia lineage. The findings provide a new resource for studying stem cell biology and neurodegenerative diseases.A study demonstrates that mammalian neural stem (NS) cells can be cultured in defined conditions without requiring a specialized niche. NS cells derived from mouse embryonic stem (ES) cells, as well as human ES cells and fetal brain, can be maintained in culture using fibroblast growth factor 2 (FGF-2) and epidermal growth factor (EGF). These cells undergo symmetrical self-renewal and retain the ability to differentiate into neurons and astrocytes. NS cells express markers of radial glia, developmental precursors of neurons and glia, and can be propagated in adherent cultures. They are capable of generating neurons upon growth factor withdrawal and maintain diploid chromosome content. NS cells derived from fetal brain and neurospheres can be expanded in culture and differentiate into neurons and astrocytes. When transplanted into the adult brain, NS cells integrate and differentiate into neurons and astrocytes. NS cells do not give rise to teratomas, unlike ES cells. They are capable of long-term survival and differentiation in both fetal and adult brain environments. NS cells can be cryopreserved and genetically modified, offering potential for genetic intervention in the nervous system. The study highlights the importance of EGF and FGF-2 in NS cell self-renewal and differentiation, and suggests that NS cells may be closely related to a radial glia lineage. The findings provide a new resource for studying stem cell biology and neurodegenerative diseases.