Brain tumor stem cells (BTSC) bear some similarities to neural stem cells (NSC). Bone morphogenetic proteins (BMPs) have a proproliferative effect on early embryonic NSC, and a prodifferentiative effect on postnatal NSC. In this issue of Cancer Cell, Lee et al. demonstrate that BMPs have differing effects on different BTSC lines, either promoting or inhibiting an astrocytic-like differentiation program. This latter effect is the result of epigenetic silencing of the BMP receptor 1B (BMPR1B). These findings document the importance of the BMP signaling system in BTSC as well as that of taking heterogeneity into account when studying BTSC as potential targets for therapy. © 2008 Elsevier Inc. All rights reserved.