Cytotoxic therapy is a cornerstone for patients with severe systemic lupus erythematosus (SLE). High-dose cyclophosphamide, 200 mg/kg, can induce a complete remission without the need for stem cell rescue in patients with autoimmune illnesses. Here we report on our first four patients treated for severe SLE with this treatment approach. Patients received cyclophosphamide, 200 mg/kg, divided over 4 days. Starting day 10, patients received filgrastim, 5 micrograms/kg/day, until their absolute neutrophil count (ANC) rose to 10.0 x 10(9)/l for two consecutive days. Disease activity as evaluated by scores from the Systemic Lupus Activity Measure-2, the SLE Disease Activity Index and the Responder Index for Lupus Erythematosus were completed before and after high-dose therapy. Before high-dose cyclophosphamide, SLE disease duration ranged from 8 to 21 (mean 12.5) years. Their average disease activity measured by SLAM-2 and SLEDAI was 15.5 (range 11-19) and 23.25 (range 20-26), respectively. At a median of 22 (range 12-39) months of follow-up, mean disease activity measured by SLAM-2 and SLEDAI decreased to 6.25 and 7.75, respectively. All patients experienced febrile neutropenia. No long-term morbidities or mortalities were observed. High dose cyclophosphamide is a therapy capable of decreasing disease severity in poor prognosis SLE patients. Future study is warranted for both refractory patients as well as primary therapy for patients with moderate to severe disease presentations.