Renal involvement in systemic lupus erythematosus (SLE) is an important cause of morbidity and mortality, reaching a prevalence of 39% during the course of the disease. Currently, the therapy for severe lupus nephritis is based on the use of high-dose corticosteroids and immunosuppressive drugs, being traditionally cyclophosphamide the most frequently used agent. Recent studies have demonstrated the efficacy of mycophenolate mofetil as induction therapy for lupus nephritis. Azathioprine, a safe drug during pregnancy, has not been demonstrated to be as effective as mycophenolate or cyclophosphamide as induction therapy, although it is an effective drug for maintenance of remission.