Haemopoietic progenitor cells are present in umbilical cord blood (UCB) and have been used to restore haemopoiesis in children after myeloablative therapy. UCB may possess a number of advantages over bone marrow and peripheral blood as a source of allogeneic progenitor cells, e.g. a lower incidence of graft-versus-host disease and a decreased risk of transmission of infection and there is considerable interest in the establishment of large cord blood banks for use in unrelated transplants. The International Conference Workshop on Cord Blood Transplantation was held in Indianapolis in November 1993 and provided a timely opportunity to review the clinical and laboratory data relating to the use of UCB in transplantation. The results from 34 UCB transplants have been reported to the International Cord Blood Transplant Registry. Engraftment was achieved in 27 of 31 evaluable patients. Graft-versus-host disease > grade 1 occurred only in children transplanted from a one haplotype matched donor; 22 patients survive at a median of 1.5 years. Further sessions at the meeting reviewed the haemopoietic cell content of UCB, the capacity for expansion of early cells and the origin (fetal and/or maternal) and function of lymphoid cells within the graft. The conference ended with a discussion of the practicalities of cord blood banking including collection, cryopreservation, storage, HLA-typing and screening for genetic and infectious diseases.