Seventy-nine hepatic allograft recipients were randomized to receive either conventional immunosuppression, including cyclosporine, azathioprine, and steroids (41 patients), or investigational therapy in which OKT3 replaced cyclosporine during the first postoperative week (38 patients). Early rejection occurred in 29 patients (71%) in the conventional group and 15 patients (39%) in the OKT3 group. Posttransplantation renal dysfunction occurred in 12 patients (29%) in the conventional group and 6 patients (16%) in the OKT3 group. Mean initial hospital stay was 34.1 +/- 18.8 days in the conventional group compared with 29.1 +/- 16.8 days in the OKT3 group. Cumulative patient survival (mean follow-up, 17.8 +/- 7.1 months) was 73.2% (30/41) for the conventional group and 84.2% (32/38) for the OKT3 group. Prophylactic OKT3 is indicated especially for liver allograft recipients with other complicating conditions that make management of early rejection unusually difficult.