Allogeneic stem cell transplantation (SCT) following myeloablative and non-myeloablative conditioning therapy has proven curative treatment for a number of inherited and acquired hematologic disorders. The success of allogeneic transplantation is largely determined by compatibility between donor and recipient, which predicts the risk of fatal graft-versus-host disease (GVHD). Unfortunately, less than one third of patients needing an allogeneic transplant have an available compatible donor in their family. Registries have been established to match patients with compatible volunteer (unrelated) donors, but many patients, and in particular minority patients, still lack stem cell donors.