code＞Purpose: The purpose of this study was to prove the effects of preemptive treatment with rituximab for Epstein-Barr virus (EBV) related post-transplant-lymphoproliferative disease ( PTLD) after hematopoietic stem cell transplantation (HSCT).br＞ Methods: We analyzed 17 pediatric patients undergoing allogeneic HSCT who developed high EBV DNAemia and were treated with rituximab (375 mg/m², once daily). All patients received HSCT at Seoul National University Children’s Hospital from 2005 to 2017. We excluded patients who had EBV infection before HSCT or were administrated rituximab after occurring PTLD. Underlying diseases of patients were 7 acute leukemia (41%), 3 aplastic anemia (18%), and the others (41%). We investigated EBV titer in peripheral blood after rituximab infusion and checked whether PTLD or not.br＞ Results: Median EBV titer just before rituximab treatment was 158,780 copies/10sup＞5/sup＞ peripheral blood mononuclear cells ( PBMCs) (range, 13,153-267,203 copies/ 10sup＞5/sup＞ PBMCs). Rituximab was infused on median 119 days (range, 16-541 days) after stem cell infusion. In all 17 patients EBV DNAemia were eradicated after median 7 days (range, 1-12 days) and PTLD did not occur in all patients. Early death occurred in 2 patients not by EBV infection/ PTLD but by acute graft versus host disease and severe venous occlusive disease. All patients excluding 2 dead patients are still alive with disease-free states without EBV reactivation after median 37 months (range, 0.5-103 months) after transplantation. br＞ Conclusion: The results of our study showed that preemptive treatment with rituximab exerts preventive effects against PTLD after HSCT by early eradicating EBV DNAemia. This study suggests one of practical preemptive treatments to decrease complications after HSCT in children./code＞