Because of the initial success of this approach, including 75 percent complete response (on no medications) in renal lupus, we are conducting a controlled trial of high-dose immunoablative cyclophosphamide versus the "gold standard" monthly IV cyclophosphamide in people with moderate to severe lupus refractory to high-dose corticosteroid therapy. We will give patients either 750 mg/m2 of body surface area IV cyclophosphamide monthly for 6 months, followed by quarterly maintenance therapy (we will readmit patients, if necessary, for infections or other complications) or cyclophosphamide 50 mg/kg/d intravenously on days 1-4. We will calculate the dose of cyclophosphamide according to ideal body weight. Patients are scheduled to receive only one course of therapy. We will follow patients according to the infective guidelines for BMT.