Slain1 was originally identified as a novel stem cell-associated gene in transcriptional profiling experiments comparing mouse and human embryonic stem cells (ESCs) and their immediate differentiated progeny. In order to obtain further insight into the potential function of Slain1, we examined the expression of beta-galactosidase in a gene-trap mouse line in which a beta-geo reporter gene was inserted into the second intron of Slain1. In early stage embryos (E7.5), the Slain1-betageo fusion protein was expressed within the entire epiblast, but by E9.5 became restricted to the developing nervous system and gastrointestinal tract. In later stage embryos (E11.5 - E13.5), expression was predominantly within the developing nervous system. Lower level expression was also observed in the developing limb buds, in the condensing mesenchyme, along the apical epidermal ridge and, at later stages, within the digital zones. These observations suggest that Slain1 may play a role in the development of the nervous system, as well as in the morphogenesis of several embryonic structures.