The number of umbilical cord blood transplants is increasing worldwide. At this time, it is important to evaluate their results and to compare the outcome of umbilical cord blood transplants with allogeneic bone marrow transplants. Data have been reported to the Eurocord Registry by multiple transplant centers. Close links have been established with the cord blood banks through Netcord. Bone marrow transplant data have been provided by transplant centers and through the European Blood and Marrow Transplant (EBMT) and International Bone Marrow Transplant Registries (IBMTR). Eurocord has analyzed the outcomes of 527 umbilical cord blood transplants from 121 transplant centers and 29 countries. The donor was related in 138 cases and unrelated in 399 cases. The results showed that survival with umbilical cord blood transplants was comparable to that with related or unrelated bone marrow transplants. Engraftment with cord blood was delayed resulting in an increased incidence of early transplant complications. The incidence of acute and chronic graft-vs-host disease was reduced with cord blood grafts even in HLA-mismatched transplants and in adults. In patients with leukemia, the rate of relapse was similar to the rate of relapse after bone marrow transplant. The overall event-free survival with umbilical cord blood transplantation was not statistically different compared to bone marrow transplants. This large registry study confirms the potential benefit of using umbilical cord blood hematopoietic stem cells for allogeneic transplants.