In 1989 E. Gluckman reported the successful cord blood transplantation in a boy with Fanconi anemia. Since then more than 1500 allogeneic cord blood transplantations have been performed worldwide. This has been possible because non-profit cord blood banks have been established that provide cryopreserved cord blood products from unrelated donors. However, cord blood transplantation is associated with specific risks that have sofar limited its more widespread use. Its main problem is the limited stem cell dose that is associated with a long aplasia and a high rate of engraftment failure. Therefore, cord blood is used as the stem cell source in only about 1 - 2 % of stem cell transplantations in childhood. The main advantage of cord blood transplantation lies in its low risk for graft-versus-host-disease (GvHD), one of the major causes for posttransplant morbidity and mortality particularly with unrelated stem cell donors. The low risk for GvHD is attributed to the low number of transplanted T cells and their functional immaturity. Another advantage of cord blood transplantation lies in the immediate availability of the cord blood units. Based on the experiences with allogeneic cord blood transplantation the indications for cord blood donation will be discussed.