Defibrotide for use in prophylaxis and/or treatment of Graft versus Host Disease (GVHD) in humans is disclosed, preferably in hematopoietic stem cell transplantation (IISCT), more preferably allogeneic hernatopoietic stein cell transplantation. Graft versus Host Disease oldie invention (GVHD) can be acute aGVHD and/or chronic cOVHD, preferably acute.