A multicenter randomized trial was performed to compare two immunosuppressive protocols after first ABO-compatible liver transplantation. Forty six patients were randomized to a 14-day treatment with Orthoclone (OKT3) in association with steroids and azathioprine, cyclosporine being progressively introduced on day 11 posttransplant. Fifty patients were randomized to a standard protocol of cyclosporine with steroids and azathioprine. Minimum follow-up was 1 year and graft and patient survivals were updated for the purpose of the study. The cumulative 1-year incidence of acute rejection tended to be greater in the cyclosporine group (75%) than in the OKT3 group (67%), especially when patients who did not receive full-course treatment with OKT3 were excluded (59%). Renal function was better preserved during the first two postoperative weeks in the OKT3 group than in the control group but plasma creatinine levels were comparable in both groups thereafter. The incidence of severe infections was lower in the OKT3 group (13.6%) than in the cyclosporine group (32%). The 4-year incidences of patient and graft survival in the OKT3 group (69% and 61%, respectively) were not different from those in the cyclosporine group (62% versus 54%, respectively). Thus this prospective trial shows that OKT3 immunoprophylaxis is a safe alternative to cyclosporine immunoprophylaxis in unselected recipients of a first liver graft.