The study reports the identification and characterization of multipotent adult progenitor cells (MAPCs) derived from human and rodent bone marrow. These cells, which can be expanded for over 80 population doublings, differentiate into mesenchymal, endothelial, neuroectodermal, and endodermal cells in vitro. When injected into early blastocysts, MAPCs contribute to most somatic cell types, and when transplanted into non-irradiated hosts, they engraft and differentiate into tissue-specific cells in the haematopoietic system and gastrointestinal tract. The findings suggest that MAPCs may be an ideal source for therapy of inherited or degenerative diseases due to their extensive proliferation and differentiation potential without senescence.The study reports the identification and characterization of multipotent adult progenitor cells (MAPCs) derived from human and rodent bone marrow. These cells, which can be expanded for over 80 population doublings, differentiate into mesenchymal, endothelial, neuroectodermal, and endodermal cells in vitro. When injected into early blastocysts, MAPCs contribute to most somatic cell types, and when transplanted into non-irradiated hosts, they engraft and differentiate into tissue-specific cells in the haematopoietic system and gastrointestinal tract. The findings suggest that MAPCs may be an ideal source for therapy of inherited or degenerative diseases due to their extensive proliferation and differentiation potential without senescence.