Oral cavity cooling (cryotherapy) provided during high-dose melphalan bolus or short-infusion administration contributes to local vasoconstriction, lower blood circulation, lower local cytotoxic drug exposure and significantly reduced oral mucositis (OM) incidence.1–3 OM is a significant posttransplant complication, and together with gut tissue damage and inflammation, caused by conditioning regimens, contributes to the development and pathogenesis of acute GVHD.4–6 The incidence of acute GVHD varies between 28 and 45% in the Flu/Mel-reduced intensity conditioning regimen comprising of fludarabine total dose 125–150mg/m2 and melphalan total dose 140–180mg/m2.1,7–9 We decided to analyze the impact of reduced OMincidence (reduced oral tissue damage) on acute GVHD, and analyzed 142 prospectively observed patients after Flu/Mel (fludarabine 30mg/m2 i.v. once daily for 4 days, melphalan 140mg/m2 i.v. one day before transplantation) allo-SCT performed at our institution from January 2005 to December 2010.