Elevated pretransplant serum ferritin levels have been associated with an increased incidence of morbidity and mortality after allogeneic haematopoietic stem cell transplantation (HCT). We studied 222 patients who underwent myeloablative allogeneic HCT in whom pretransplantation serum ferritin levels were available. Pretransplantation ferritin > 1910 microg/l was associated with lower overall survival (P = 0.003), lower relapse-free survival (P = 0.003), decreased chronic graft-versus-host disease (GVHD) (P = 0.019) and increased non-relapse mortality (NRM) (P = 0.042). Similar results were obtained when pretransplantation ferritin was analysed as a continuous variable and by quartiles. Our results indicate that an elevated pretransplant ferritin level adversely impacts transplantation outcomes. The adverse impact of elevated ferritin on NRM and survival was despite its association with lower incidences of acute and chronic GVHD, which are major causes of NRM. The association of ferritin with iron overload and its influence on HCT outcomes requires further prospective validation.