Tfap2d encodes a novel member of the AP-2 family of transcription factors, called Ap-2 delta. Ap-2 delta has a unique DNA sequence binding specificity and lacks a PY motif as well as several highly conserved residues in the transactivation domain that are essential for transcriptional activation for other AP-2 proteins. In this study, we characterized the expression pattern of Tfap2d in mouse embryos from E7.5 to E16.5 using in situ hybridization as a first step towards understanding the role of Ap-2 delta during development. Overall, Tfap2d is expressed with a more restricted temporal and spatial pattern than the other Tfap2 genes, with signals observed in the central nervous system, retina, and, uniquely, in the developing heart. Signals were not detected in tissues such as the neural crest, facial mesenchyme, and limbs where the other Tfap2 genes are expressed. The expression of Tfap2d was first noted at E9.5, later than other Tfap2 genes, with signals from the heart and brain. The expression in the developing myocardium persisted through E10.5. Expression of Tfap2d was diffuse in the developing brain at E10.5 to E11.0, but became restricted to the roof of the third vesicle with two narrow columns extending forward along the wall of the third vesicle and the roof of the heopallial cortex in the forebrain from E12.5 onwards. Tfap2d expression was also observed in the spinal cord at E10.5. From E13.5 to E16.5, Tfap2d was expressed in the retinal epithelium. Based on Tfap2d's unique expression pattern and functional features, we believe that Ap-2 delta plays a role during mammalian development that is non-overlapping with those of the other Ap-2 transcription factors.