Corticosteroid-resistant graft-versus-host disease (GvHD) is difficult to manage and is associated with high morbidity and mortality. The purpose of our study was to evaluate the safety and efficacy of mycophenolate mofetil (MMF) as the salvage therapy for steroid-refractory GvHD. Twenty one patients (10 with acute GvHD and 11 with chronic GvHD) were studied retrospectively. Steroid-resistant GvHD was defined as acute or chronic GvHD not responding to a first-line regimen of cyclosporine A and corticosteroids in a dose equivalent to 2 mg/kg methylprednisolone for at least 7 days. MMF was added at a dose of 2 g daily, and corticosteroids were tapered. Thirteen (62%) of 21 patients responded to the treatment with MMF, including 6 (60%) of 10 patients with acute refractory GvHD and 7 (64%) of 11 patients with chronic refractory GvHD. The most common adverse effects were infectious complications (67%, 14 of 21 patients) and hematological toxicity (29%, 6 of 21 patients). Median duration of MMF administration was 6 months (range 1-27 months). Sixteen of 21 patients were alive after the median follow-up of 27 months (range 1-72 months) after the initiation of MMF therapy. All 16 surviving patients were in good clinical condition and in remission of their hematological malignancy. Five patients died--two of relapses of leukemia and three of refractory intestinal GvHD. These results suggest that MMF can be an effective treatment for some cases of steroid-refractory GvHD.