Patients receiving standard cyclosporine therapy will receive a full dose of the drug for at least 3 months. Those taking both cyclosporine and MMF will take MMF plus half-dose cyclosporine for 3 months and continue MMF for an additional 6 months. Both drugs are taken twice a day by mouth. All patients will have about 120 milliliters (4 ounces) of blood drawn at the beginning of the study to evaluate immune system activity and bone marrow function, and to look for genetic material of certain viruses. Bone marrow aspirations and biopsies will be done at the beginning of the study, and at 6 and 12 months. For these tests, the area of the hip is anesthetized and a special needle is used to draw bone marrow from the hipbone.