Pluripotential stem cells from livestock offer an exciting prospect for the biotechnology industry. Applying strategies established for the derivation of murine induced pluripotential stem cells (iPSCs), we have isolated ovine iPSCs that can give rise to cells characteristic of all three germ cell layers both in vitro from embryoid bodies and in teratomas in vivo. Furthermore, although at a low level, these ovine iPS cells can contribute to live-born chimeric lambs. Colonies derived from ovine embryonic fibroblasts transfected with murine cMyc, Klf4, Oct4, and Sox2 displayed smooth domes with sharp edges when grown in human embryonic stem cell (ESC) medium but not in mouse ESC medium. These ovine iPSCs were alkaline phosphatase positive, expressed Nanog, and had a normal karyotype. These cells represent an important step in the understanding of mechanistic nature of pluripotency in ungulates.