Mycophenolate mofetil (MMF) has recently been introduced as an immunosuppressive agent for the treatment of glomerulonephritis with systemic lupus erythematosus (SLE) and the data have been encouraging. However, response to MMF treatment appears to differ ethnically. Therefore, we determined efficacy and safety of low-dose MMF for Taiwanese patients with lupus nephritis. We studied 36 lupus nephritis patients who were treated with MMF. The dose started at 0.5 g/day and we collected the data from patients who received up to 1 g/day MMF. Outcome measures were 24 h for proteinuria, serum creatinine, C3/C4 levels, and anti-dsDNA titers collected at the baseline and at 3-month treatment intervals. Daily urinary protein significantly decreased from 6.15 +/- 4.28 g to 2.69 +/- 2.36 g at the last visit (P < 0.01) in spite of the significant absence of changes in serum creatinine levels. The response rate was 65.7% including five (14.3%) cases of complete remission and 18 (51.4%) cases of partial remission. The concomitant oral prednisolone dose decreased significantly from 20.07 +/- 11.78 mg/day to 13.93 +/- 6.79 mg/day at 6 months (P < 0.01). The level of C3 increased significantly from 59.46 +/- 32.73 to 71.99 +/- 25.81 (P < 0.01) and the anti-dsDNA antibody titer decreased from 161.71 +/- 221.42 to 46.57 +/- 117.47 (P < 0.01). No severe adverse effects were observed in the study. Low-dose MMF (0.5 to 1 g/day) combined with glucocorticoids appears to be a safe and effective therapy for lupus nephritis in Taiwanese patients. Our results suggest that lupus nephritis in Oriental patients might respond to lower doses of MMF than Caucasians.