Over the last decade, a number of studies have provided evidence of the existence of stem cells with pluripotency properties either in fresh bone marrow or following in vitro culture. Numerous groups have isolated non-hematopoietic cell populations from bone marrow, umbilical cord blood, amniotic fluid or fetal tissue via in vitro culture, which possess some molecular and biological properties comparable to embryonic stem cells. Due to their differentiation capacity into cells with features of the three germ layers, they are a novel cellular source for tissue regeneration. Because such stem cells of greater potency can be expanded for prolonged periods ex vivo without evidence of senescence and can be easily genetically manipulated, they can also be considered good candidates for gene therapy approaches.