The orphan nuclear receptor TLX promotes neural stem cell self-renewal, but its role in hippocampal neurogenesis is not known. Murai et al. generated transgenic (Tg) mice in which TLX expression was placed under the control of the promoter for nestin, a marker of neural precursors. Adult Tg mice exhibited increased numbers of proliferating neural progenitors and 5-bromodeoxyuridine-labelled newborn neurons in the dentate gyrus compared with wild-type mice, and performed better in the Morris water maze, a test of spatial learning and memory. Thus, TLX expression in neural progenitors cells is important for adult hippocampal neurogenesis and memory.