Although recent studies on adults with lupus nephritis indicate that mycophenolate mofetil (MMF) may be effective in maintaining remission for patients who previously received short-term intravenous cyclophosphamide (IVCY) induction therapy, the experience with the new immunosuppressive agent in children with severe lupus nephritis has not been as satisfactory thus far. To assess the efficacy and safety of maintenance therapy with MMF, we prospectively analyzed four patients with biopsy-proven severe lupus nephritis (three girls, one boy; mean age 12 years; two with class IIIA, two with class IVG(A); mean duration of lupus nephritis 7 months) receiving MMF for at least 6 months after induction treatment. These patients had been treated previously with 6 months of low-dose IVCY combined with oral mizoribine and steroids for induction, followed by therapy with MMF adjusted to maintain predose mycophenolic acid (C0-MPA) levels at 2-5 mcg/ml. Mean follow-up after staring MMF was 27.5 months (range 6-41). The mean MMF dose required was 405 +/- 49 mg/m(2) per 12 h, which maintained mean C0-MPA levels of 3.3 +/- 0.41 mcg/ml. No patient experienced renal flares during maintenance therapy with MMF, which permitted a significant reduction in mean prednisolone dose from 11.9 +/- 1.3 to 3.9 +/- 2.6 mg/day (P = 0.003). No significant gastrointestinal or hematologic side effects of MMF were noted. This preliminary study demonstrates that maintenance therapy with MMF after a low-dose IVCY regimen appears to be a promising intervention without adverse effects in children with severe lupus nephritis. These data should be confirmed by a prospective randomized multicenter clinical trial.