Liver allograft survival rates of 50% to 60% are reported in blood group A, group B, group O (ABO)-incompatible mismatched grafts even when aggressive immunosuppressive protocols, including plasmapheresis, OKT(3), cyclophosphamide, cyclosporine, prostaglandin E(1), and steroids, are used. A 59-year-old woman, blood type O(+), required emergency retransplantation posttransplantation day 2 because of primary nonfunction of the liver allograft. A blood type AB(+) allograft was used. Induction immunosuppressive therapy included tacrolimus, mycophenolate mofetil, OKT(3) (muromonab-CD(3)), steroids, and prostaglandin E(1). In addition, plasmapheresis was performed daily for 9 days. OKT(3) and prostaglandin E(1) were also discontinued postoperative day 9. Biopsy-proven acute cellular rejection was diagnosed postoperative day 12 and was treated with double-dose OKT(3) (10 mg) for another 6 days. On the day OKT(3) was discontinued, daclizumab, 60 mg, was administered intravenously. This dose was repeated every 2 weeks for a total of 5 doses. At 1-year follow-up, the patient is doing very well with normal liver function. We are unaware of previous reports of the use of daclizumab and mycophenolate mofetil as part of an immunosuppressive protocol aimed to induce acceptance of ABO-incompatible mismatched liver allografts. Based on our experience with this case, it seems that mycophenolate mofetil is an adequate replacement for cyclophosphamide. We also believe daclizumab provided adequate protection at a critical time. Further experience with both these drugs is required to establish their role in ABO-incompatible mismatched liver allografts.