The treatment of severe lupus nephritis is based on the combination of steroids and cytotoxic drugs. Intravenous cyclophosphamide administered in "pulses" is effective in the induction of remission but other therapeutic alternatives are sought in refractory cases or severely relapsing patients. Mycophenolate mofetil, used in renal transplantation, also can be useful in severe lupus nephritis. We describe the evolution of 6 patients (5 women and 1 man; age 17-45 years) with severe lupus nephropathy who after achieving remission with intravenous cyclophosphamide and steroids (5 cases) or cyclosporin A (1 case) showed relapse of proteinuria and were treated with mycophenolate mofetil (dose 1000-2000 mg/day). Two patients have completed 24 months, 1 patient two cycles of 12 months, 2 patients 18 months and 1 patient 6 months. After this treatment, all patients have achieved remission (3 partial and 3 complete). There was no treatment failure and no one patient discontinued medication; however 1 case relapsed. There were no changes in leucocytes, haemoglobin, serum creatinine and serum albumin. ANA and alpha DNA antibodies decreased. Proteinuria (measured as protein/creatinine urine ratio: initial 3 and final 0.3) and dose of steroids (initial: 17.5 mg/d and final 5 mg/d) decreased significantly (p < 0.05 Wilcoxon t-test). The most common side effects were nausea and abdominal discomfort that improved without discontinuation of treatment. We conclude that mycophenolate mofetil is effective and a safe drug in severe relapsing lupus nephritis.