Neural stem cells are known to give rise to distinct subtypes of neurons and glial cells over time by changing their competency. However, precise characterization of neural stem cells at various developmental stages remains to be performed. For such analysis, a tool to manipulate neural stem cells at different time points is necessary. Here, we generated transgenic mice that express Cre‐ER^T2 in the ventricular zone of the developing nervous system under the control of the nestin promoter and enhancer (Nes‐CreER^T2). In mice expressing Cre‐ER^T2 at appropriate levels, Cre recombinase activity was mostly inactive but efficiently activated by tamoxifen within 1 day. When such mice were crossed with the ROSA‐26 or Z/EG reporter mice, neural stem cells were permanently labeled after administration of tamoxifen. Thus, Nes‐CreER^T2 mice offer a powerful tool to manipulate neural stem cells genetically at desired time points. genesis 44:233–238, 2006. © 2006 Wiley‐Liss, Inc.