Here, we show that Multi-potent Adult Progenitor Cells (MAPCs) can be derived from adult and fetal swine bone marrow. Swine MAPC (swMAPC) contain initially multiple different progenitors and mature cells; however, cultures are homogenous by 50 population doublings and can grow past 150 population doublings. SwMAPCs are CD44, CD45, and MHC-I, II negative, express Oct3a/4 at levels close to those seen in embryonic stem cells, and have telomerase activity leading to no telomere shortening with expansion. We also have very solid evidence that swMAPCs differentiate into most mesoderm, neuroectoderm, and endoderm lineages as demonstrated by a significant up-regulation of transcription factors and other lineage specific proteins in a time dependent fashion similar to development, measured by Q-RT-PCR as well as immunohistology. In addition, swMAPCs induced to the endothelial lineage form vascular tubes, to the hepatic lineage produce albumin and urea, and to the smooth muscle lineage display significant calcium flux in response to smooth muscle agonists. In addition, we are investigating the swMAPC differentiation into cardiomyocytes. Preliminary data indicates swMAPCs express TBX5, Nkx2.5, and GATA6 by day 7 at significant levels. As we have seen for rodent MAPCs, when swMAPCs are allowed to grow at high density, Oct3a/4 levels drop to undetectable ranges, the cells take on a mesenchymal stem cell (MSC) phenotype, and the differentiation potential is lost. When replated under low density conditions, oct3a/4 expression or differentiation capacity can not be re-induced, and cells remain MSC like. Therefore, we suggest that Oct3a/4 is not an in vitro culture phenomena but is already present in swMAPCs and cannot be recovered once lost with standard culturing techniques.