Mycophenolate mofetil is a new immunosuppressive drug which acts by impairment of de-novo purine synthesis. 1 The drug is relatively selective for lymphocytes and inhibits antibody production by B cells1 more than other immunosuppressants. Mycophenolate mofetil proved to be a potent immunosuppressant for prophylaxis and treatment of renal-transplant rejections with a favourable side-effect profile. 2 In patients with systemic vasculitis associated with antineutrophil cytoplasmic antibodies (ANCA), induction therapy with oral corticosteroids and cyclophosphamide is usual. 3 The use of cyclophosphamide in maintenance therapy has come under discussion, since a retrospective analysis raised concern about serious long-term complications. 4 Therefore, with informed consent, we treated four patients with systemic vasculitis with mycophenolate mofetil 2 g daily in combination with oral corticosteroids as maintenance therapy after standard induction therapy (cases 1–4, table). There were no relapses of vasculitis. ANCA titres decreased in all four patients and mycophenolate mofetil was well tolerated. The success of mycophenolate mofetil in maintenance therapy of systemic vasculitis encouraged us to try the same approach in patients with IgA nephropathy (IgAN)(cases 5 and 6, table). Humoral immunity is believed to play a pivotal role in the pathogenesis of IgAN. 5 To date, there is no therapy for IgAN and end-stage renal failure is the outcome in 30% of patients. 5 Predictors of a poor outcome are renal insufficiency, proteinuria, and hypertension. 5 Therefore we used mycophenolate mofetil, after obtaining informed consent, to treat high-risk patients with IgAN. A 42-year-old man (case 5) had recurrent IgAN in his renal allograft reflected by urine sediment, proteinuria, and a declining creatinine clearance. Mycophenolate mofetil 2 g daily was added to the patient’s maintenance immunosuppression with cyclosporin and 12· 5 mg daily of prednisolone. Proteinuria started to fall 2 weeks after initiation of mycophenolate mofetil and reached a stable level of 0· 5 g daily after 4 months of treatment. A 53-yearold woman (case 6) had rapidly progressive IgAN. Oral corticosteroids were administered at a dose of 1 mg/kg daily. Renal function recovered immediately with serum creatinine falling from 619 µmol/L to 150 µmol/L within 4 weeks. When the patient was seen again after 4 months of oral steroids she had developed diabetes mellitus and Cushing’s syndrome. Reduction of steroids below 20 mg daily, however, had provoked rises in the creatinine. Mycophenolate mofetil 2 g daily was started and the steroids were tapered then omitted 5 weeks later. 4 months after switching to mycophenolate mofetil, her diabetes mellitus and proteinuria had disappeared and creatinine had returned to normal.