Although chemoimmunotherapy -based treatments have improved the survival of patients with HLH, outcomes of the patients are still unsatisfactory. Retrospective nation—wide data recruitment for the pediatric HLH patients diagnosed between 1996 and 2011 was carried out by the Histiocytosis Work-ing Party of the Korean Society of Hematology. Twenty-five patients who received HSCT among the total of 274 enrolled children with HLH were analyzed for the transplant-related variables and events. Condition-ing regimen included Busulfan(Bu)/ Cyclophosphamide(Cy)/etoposide with or without ATG (n=15), Bu/flu-darabine/ATG (n=3), fludarabine/melphalan with ATG or alemtuzumab (n=4), and other combinations in 3. The probability of 5-year overall survival (OS) after HSCT was 75.8％ with a median follow-up of 84 months. The reasons for HSCT were active disease after 8 weeks of initial treatment in 11 patients, familial HLH (FHL) in 8, and reactivated disease in 6. Nineteen patients are currently alive without disease after HSCT, whereas 5 patients died of treatment-related events at early post-transplant period (graft failure in 3, GVHD in 1 and CMV pneumonitis in 1), and 1 patient died of reactivation at 1 year post transplanta-tion. The survival of patients who were transplanted because of active disease after 8 weeks of initial treat-ment was inferior compared to that of patients who had inactive state at that time (61.9％ vs. 100％, re-spectively, P=0.04). Patients who received cord blood graft (n = 6) showed significantly inferior OS than those who received bone marrow (n=15) or peripheral blood graft (n=4) (33.3％ vs. 86.7％ vs. 100％, P= 0.016). Four patients of the 6 who received transplants using cord blood died (graft failure in 2, reactiva-tion in 1 and GVHD in 1). The 5-year OS rate after HSCT according to the donor type was 87.5％ for the matched related donors (MRD) (n=8) and 70.1％ for the unrelated donors (UD) (n=17) (P = 0.398). HSCT improved the survival of the patients who had familial, reactivated, or severe and persistent secondary HLH in the Korean nation-wide HLH registry. The disease state after initial treatment and the stem cell source of the transplant were 2 important prognostic factors that influenced the OS of the HLH patients who un-derwent HSCT.