Allogeneic bone marrow transplantations (BMT) from HLA-matched siblings have been successfully used for treatment of patients with high-risk hematological malignancies, genetic immunodeficiencies, metabolic disorders, or marrow failure syndromes. Unfortunately, most of patients lack matched related donors. Over the past decade clinicians have explored the suitability of umbilical cord blood (CB) as an alternative source for hematopoietic stem cell transplantation. Since the first related cord blood transplantation (CBT) was performed successfully for a child with Fanconi Anemia in 1988, there have been many children undergoing CBT from related donors. The further experience suggests that CB donation is a safe procedure for both mother and newborn. Subsequently, several quality CB banks were established worldwide with requirement of specific issues including donor recruitment, CB collection and processing, histocompatibility testing, infectious and genetic disease testing, transportation of CB, and protection of confidentiality of donors and recipients. The clinical data showed that unrelated donor CBT had comparable survival results to unrelated donor BMT CB offers many potential advantages such as it is readily available, its collection causes no harm to the donor and minimal HLA-disparity is acceptable. However there are some disadvantages due to the volume and cell dose of each collected CB is limited, thus methods to enhance the number or quality of stem cells in CB are needed. At present the world's experiences suggest that CB is an acceptable alternative to bone marrow.