Eight patients with resistant and/or relapsing nephrotic syndrome or renal insufficiency were empirically treated with mycophenolate mofetil (MMF). The underlying glomerular diseases were membranous nephropathy (N = 3), minimal change disease (n = 2), focal segmental glomerulosclerosis (n = 1), and lupus nephritis (N = 2). Treatment with MMF 0.75 to 1.0 g twice daily, either as monotherapy or in combination with low-dose steroid treatment, resulted in substantial reductions in proteinuria or stabilization of serum creatinine. In relapsing patients following withdrawal from cyclosporin A, MMF achieved suppression of proteinuria equivalent to or better than that which occurred during cyclosporin A treatment. Steroids were successfully withdrawn in each of the non-lupus patients. MMF was well tolerated with no evidence of hematologic, hepatic, or other toxicity. These clinical anecdotes demonstrate the short-term clinical efficacy of MMF treatment. In addition, they suggest that MMF may have major steroid-sparing effects and might represent an alternative to cyclosporin A in appropriate patients.