Lupus is a disease of the immune system that can damage many body organs. Damage to the kidneys from this disease is known as lupus nephritis. Lupus nephritis is difficult to treat and can return even if initial treatment is successful. If left untreated, lupus nephritis can progress to complete kidney failure. Patients with kidney failure need kidney transplantation or hemodialysis (a procedure in which a special machine filters the blood). Treatment of lupus nephritis often includes two powerful drugs that suppress the immune system: methylprednisolone and cyclophosphamide. Both of these drugs can have serious side effects. An earlier study showed that cyclophosphamide, either alone or in combination with methylprednisolone, was more effective than methylprednisolone alone in the short term (< 5 years). At the end of 5 years, patients who received the combination seemed to do better than the other groups, but these results were not clear cut. It is not known what happens after 5 years to patients treated with these drugs.