The purpose of this trial is to study the effectiveness of an immunosuppressive drug, sirolimus, in the treatment of chronic graft versus host disease in combination with prednisone. Graft versus host disease (GVHD) is a common complication in patients who have received blood or marrow transplantation from a related or unrelated donor. Chronic GVHD occurs approximately 100 days after transplantation and is the result of the donor immune system recognizing the patient's tissues as foreign and creating harmful effects on the patient's organs. We hope the use of sirolimus will decrease the significant disabling effects and deaths caused by chronic GVHD.