The ability to identify, select and manipulate stem cells from tissues opens the way to regenerative medicine. In the field of hematopoiesis, our increasingly precise knowledge of the mechanisms of production and regulation of blood cells should permit in the near future the production of cells in sufficient quantity to be of interest for transfusion. Our present capacity to amplify hematopoietic stem cells and direct their differentiation towards the erythroid line is reviewed here. A procedure is described for the amplification of CD34 + hematopoietic stem cells of placental origin, based on the sequential use of specific combinations of growth factors in a given serum-free medium. Such conditions allowing the terminal maturation in vivo of large numbers of precursors produced ex vivo permit one to envisage important transfusion perspectives. A complementary source of red blood cells would in fact improve our transfusion capacity.