Umbilical cord blood (UCB) is an alternative source of hematopoietic progenitors and has potential advantages over bone marrow. We present our experience with UCB transplants performed between July 1994 and June 1997 in seven children with hemoblastosis. Two patients underwent transplantation from an HLA-identical sibling donor and five from an unrelated donor. Engraftment was obtained in all but one patient. Acute GVHD was absent in patients with related donors and present in all patients with unrelated donors. No patient showed chronic GVHD. Two patients died from transplant-related complications and a further two relapsed. Four patients were alive with a follow-up of 14, 15, 21 and 39 months post-transplant, respectively. Overall survival was 57% (s.e. 0.19). We conclude that cord blood is a good alternative source of hematopoietic stem cells for children with malignant hematologic diseases.