Since the introduction of OKT3 at our center in January 1986, we have performed 246 cadaveric renal transplants (220 primary, 26 nonprimary). All patients received quadruple immunosuppression consisting of prednisone, azathioprine, and the sequential use of Minnesota antilymphoblast globulin (MALG) and cyclosporine. OKT3 (Orthoclone OKT3) therapy was reserved for corticosteroid- and/or ALG-resistant rejection. Of the 246 patients, 138 developed one or more rejection episodes (56.1%). Ninety-seven (70.3%) were successfully reversed with prednisone and/or ALG, whereas 41 (29.7%) required additional treatment with OKT3. Initial graft salvage occurred in 34 (82.9%) patients treated with OKT3, but rejection recurred in 18 (52.9%) and was successfully reversed in only 6 patients. However, the rate of recurrent rejection was much lower in patients given OKT3 early (14%), shortly after it was apparent that high-dose corticosteroid therapy was proving ineffective, than in patients who received OKT3 after a prolonged or second course of corticosteroids (64%) or ALG (60%). Graft survival after a mean follow-up interval of 11 months in all OKT3-treated patients was 54%. One or more infections occurred in 19 (46%) patients treated with OKT3. Patients developing infections following OKT3 therapy received significantly larger total doses of prednisone during graft rejection (46.3 mg/kg vs. 27.9 mg/kg, P less than .05) than OKT3-treated patients who did not develop infectious complications. Our experience shows that use of OKT3 for treatment of corticosteroid- and/or ALG-resistant rejection is associated with a high rate of recurrent rejection, except when given early, as soon as it is clear that high-dose corticosteroid therapy is not reversing the rejection episode. It further suggests that prolonged administration of high-dose corticosteroids and possibly ALG for the treatment of rejection prior to beginning OKT3 greatly increases the rate of infection following OKT3 therapy.