Graft versus host disease (GVHD) is the most ominous side effect of allogeneic bone marrow or blood stem cell transplantation (BMT). GVHD causes a severe inflammatory process, which affects primarily the skin and the GI) system, including the liver. Pharmacological treatment of GVHD includes various immunosuppressive and immune-modulating drugs, including steroids, cyclosporin, tacrolimus, methotrexate and anti-lymphocyte agents. These agents can aggravate immunologic incompetence, exposing the patient to infections and secondary malignancy, as well as reducing the efficacy of graft versus leukemia / graft versus tumor (GVL / GVT) effects induced by alloreactive donor lymphocytes. In spite of this effect on the immune system, only 50-70% of the patients achieve partial control of GVHD, which can rapidly deteriorate and result in death. Despite the use of innovative immunosuppressive modalities, the prognosis of steroid resistant GVHD is usually poor. GVHD can be mostly localized to a specific organ (skin, liver, GI) with liver involvement tending to be more chronic and resistant. The bile ducts are the main target for GVHD, with their blood supply originating from the hepatic artery. This may explain the ineffective nature of oral steroids absorbed through the gut into the portal vein.