Background: Our study characterizes Delta-like 1 (Dll1) in the adult mouse, particularly in normal versus injured vasculature, with the aid of the transgenic Dll1<sup>LacZ</sup> line. Methods: Normal mouse adult tissues or those from the Dll1<sup>LacZ</sup> reporter line were analyzed for Dll1 expression and promoter activity. Vascular tissue was analyzed before and after carotid artery ligation. Results: In wild-type mice, Dll1 transcript expression was widespread. Similarly, the Dll1<sup>LacZ</sup> reporter had β-galactosidase activity detectable in the cerebellum, cerebrum, spinal cord, liver, lung and cornea, although the normal adult vasculature had no reporter expression. Following arterial ligation, there was acute induction of Dll1<sup>LacZ</sup> reporter expression, both in the ligated left carotid artery, and the uninjured right contralateral artery. Expression returned to low/undetectable levels 4–10 days after arterial ligation. Conclusion: The expression of Dll1 in the adult mouse is more widespread than previously realized, although not in resting large arteries in the adult mouse. Following arterial injury, Dll1 promoter activity is induced selectively in the endothelial cells of both the injured artery and the contralateral uninjured artery. Our results show that while overall expression in the adult mouse is widespread, Dll1 may be selectively expressed in the endothelium of injured vasculature, similar to the endothelial-restricted expression of Dll4.