In utero stem cell transplantation represents a new and still experimental therapeutic strategy for diseases related to the hematopoietic system, i.e. hemoglobinopathies, immunodeficiency diseases and metabolic disorders. To date, a total of 21 cases of transplantations using stem cells either of fetal liver or adult bone marrow origin have been reported in the literature. Success has been limited--with the exception of one case of beta-thalassemia--to four cases with immunodeficiency diseases. In this review the broad therapeutic implications as well as potentials and limitations of this technique are summarized. Furthermore, ethical considerations based on the use of fetal cells are pointed out and a prospective view concerning experimental and clinical future perspectives including the possibility for gene therapy is presented.