Neural stem cells (NSCs) are multipotent progenitor cells that possess the ability to self-renew and generate different neural cell types. Bone morphogenetic proteins (BMPs) play critical roles in the determination of the fate of NSCs. Although some reports delineate BMP expression in the early developing central nervous system (CNS) they deal mainly with its expressions in restricted areas. However, little information is available for BMP expression in NSCs and their lineages. In this study, based on an in vitro model in which NSCs can self-renew and differentiate into astrocytes, neurons or oligodendrocytes, we mimicked the environment of NSC development in vivo. Using an antibody which can recognize BMP-2 and BMP-4, we showed that BMP-2/4 is only expressed in astrocytes. Inflammatory cytokines (tumor necrosis factor-alpha and/or interferon-gamma) do not influence the expression pattern of BMPs in NSCs and their lineages. These results suggest that astrocytes might be one source of BMPs during the differentiation of NSCs and in the inflammatory environment after CNS injury.