Delayed graft function remains a major problem in cadaveric renal allograft transplantation. We have used 2 different immunosuppressive induction regimens in patients with delayed graft function. The first regimen, used in 40 patients from January 1985 to December 1986, consisted of CsA (8 mg/kg/day, orally within 48 hr of cadaveric renal transplantation regardless of graft function), azathioprine (1.5-2.5 mg/kg/day), and steroids (methylprednisolone 375 mg on day 0, then prednisone tapered to 30 mg/day by day 10 with slow tapering to 7.5-10 mg/day over the first 6 months after transplantation). A second regimen, used from January 1987 to March 1989, employed the same doses of azathioprine and steroids; however, OKT3 (5 mg i.v./day for 7-21 days) was administered in the 34 patients who had delayed graft function. CsA was withheld until ATN resolved. The use of OKT3 as induction immunosuppression in patients with ATN led to a significant increase in 1-year graft survival (80% vs. 55%) while markedly decreasing the incidence of rejection episodes (44% vs. 82%) and the duration of nonfunction (9.4 vs. 14.9 days). There were 5 CMV infections in patients treated with OKT3. Antibodies to OKT3 developed in only 1 of 34 patients treated with OKT3. Five of 7 patients who received a second course of OKT3 successfully reversed the rejection episode. Patient survival (89%) was the same in the 2 groups. The benefit of OKT3 on long-term graft survival appears to stem from elimination of early rejection episodes that may be difficult to diagnose in a poorly functioning allograft. We conclude that OKT3 induction provides superior results over CsA induction at doses given in renal allograft recipients with delayed graft function without a significant increase in morbidity or mortality and permits the reuse of OKT3 for treatment of rejection in most cases.