Iron overload might be an important contributor to nonrelapse mortality (NRM) in hematopoietic stem cell transplantation (HSCT). We studied 264 patients undergoing allogeneic HSCT for hematologic malignancies between 1996 and 2006, using pretransplantation serum ferritin as a surrogate marker of iron overload. At 5 years, patients in the high ferritin group (>or= 599 ng/mL) had a lower overall survival (OS; 33.0% versus 63.5%; P< .001) and a higher NRM (34.9% versus 13.7%; P< .001) than those in the low ferritin group (<599 ng/mL). Multivariate analyses showed that high pretransplantation serum ferritin was a significant risk factor for worse survival (relative risk [RR]=1.68; P= .05) and increased NRM (RR=2.47; P= .01). There was no significant difference in the cumulative incidence of relapse, and acute and chronic graft-versus-host disease (aGVHD, cGVHD) between the 2 groups. Patients in the high ferritin group were more likely to die of infection (P< .010) and organ failure (P< .019). Similar results were observed after dividing the patients according to the intensity of conditioning regimens. These findings emphasize the prognostic impact of pretransplantation serum ferritin in HSCT recipients.