Norovirus infections are increasingly being recognized as important causes of diarrhea in hematopoietic stem cell transplantation (HSCT) recipients. This retrospective study aimed to evaluate the cumulative incidence, risk factors, and outcomes of norovirus infection in pediatric HSCT recipients. Among 55 patients age <21 years who underwent first HSCT between July 2007 and June 2011, 49 patients developed diarrhea and had stool tested for norovirus. Eight of these patients were found to be infected with norovirus. All were sporadic cases and manifested with nausea, vomiting, and diarrhea. The median age of these patients was 5.2 years (range, 0.5-18.5 years). Six were males. Seven patients underwent unrelated donor HSCT, and 1 patient underwent autologous cord blood HSCT. Two patients had norovirus infection before HSCT that persisted after transplantation. In the remaining 6 patients, norovirus developed at a median of 36.5 days posttransplantation (range, 5-517 days). The cumulative incidence of norovirus infection was 12.9% at 2 years posttransplantation. Risk factors for norovirus infection included the use of peripheral blood or cord blood as the stem cell source (P = .043) and administration of fludarabine (P = .002) and alemtuzumab (P = .011). The median time to viral clearance was 145 days (range, 13-263 days). Four-year survival was similar in norovirus-infected patients and noninfected patients (56.3% versus 58.3%). Copyright © 2012 American Society for Blood and Marrow Transplantation. Published by Elsevier Inc. All rights reserved.