This study demonstrates that neural stem (NS) cells can be derived and continuously expanded in a defined culture system using fibroblast growth factor 2 (FGF-2) and epidermal growth factor (EGF). The combination of EGF and FGF-2 is sufficient to support symmetrical self-renewal and maintain the ability to differentiate into neurons and astrocytes. NS cells derived from mouse embryonic stem (ES) cells or foetal brain exhibit uniform expression of radial glia markers and can be passaged continuously without differentiation. These cells also show efficient engraftment and differentiation in the adult mouse brain, suggesting their potential for therapeutic applications. The findings provide a new resource for studying tissue-specific stem cells and comparing them with pluripotent ES cells.This study demonstrates that neural stem (NS) cells can be derived and continuously expanded in a defined culture system using fibroblast growth factor 2 (FGF-2) and epidermal growth factor (EGF). The combination of EGF and FGF-2 is sufficient to support symmetrical self-renewal and maintain the ability to differentiate into neurons and astrocytes. NS cells derived from mouse embryonic stem (ES) cells or foetal brain exhibit uniform expression of radial glia markers and can be passaged continuously without differentiation. These cells also show efficient engraftment and differentiation in the adult mouse brain, suggesting their potential for therapeutic applications. The findings provide a new resource for studying tissue-specific stem cells and comparing them with pluripotent ES cells.