We have created a transgenic mouse line that expresses Cre recombinase under the control of the novel mouse promoter/enhancer D6. We describe the expression pattern of D6-Cre in a Gtrosa26 reporter background as assayed by LacZ activity. The enhancer activity starts at 10.5 days post-coitum in the telencephalon and is at the later embryonic stages highly restricted to the hippocampus and the neocortex. In adult mice D6-derived cells are found in cortical layers II-VI, in the granular cells of the dentate gyrus and in hippocampal fields CA1-CA3. D6-Cre activity is also detected in the ependymal and subependymal zone of the lateral ventricles which is known to harbor neural stem cells.