Mycophenolate mofetil (MMF) has been used successfully as an immunosuppressive agent after kidney and heart transplantation, but experience with MMF after liver transplantation is still limited. Between August 1995 and January 1996, we treated 20 patients with MMF after orthotopic liver transplantation in an open, prospective study. Five out of eight patients with acute rejection and one patient with early chronic rejection showed a complete response after MMF was added to the immunosuppression. Three patients with chronic rejection did not improve, one died, and two have stable graft function at present. In eight patients who suffered from toxicity, a reduction in the dosage of tacrolimus was attempted with simultaneous MMF therapy. One patient died due to multiple organ failure. Liver function improved completely in one other patient, and partially in three patients after adding MMF. In the remaining three patients, a reduced dosage of tacrolimus or cyclosporin, together with MMF, reduced toxicity, not significantly. In conclusion, MMF appears to be a safe and potentially useful adjuvant immunosuppressive agent for rescue and maintenance therapy.