This article discusses the pluripotency of mesenchymal stem cells derived from adult marrow. It reports that cells co-purifying with mesenchymal stem cells differentiate not only into mesenchymal cells, but also cells with visceral mesoderm, neuroectoderm and endoderm characteristics in vitro. As they proliferate extensively without loss of differentiation potential, and they may be an ideal cell source for therapy of inherited or degenerative diseases.