Recent studies have documented the efficacy of quadruple immunotherapy with sequential ALG/cyclosporine in cadaveric renal transplantation. However, the exact role of ALG in this regimen is controversial. Over a four-year period, we performed 429 cadaveric renal transplants (367 primary, 62 retransplants) with prednisone, azathioprine, and the sequential use of Minnesota antilymphoblast globulin (MALG) and CsA. ALG therapy was divided into three protocols: true sequential (n = 259, mean no. days of ALG = 8.2); extended (defined as sequential MALG/CsA continued for 14 days irrespective of renal function or CsA level, n = 103, mean no. days of ALG = 14.1); and therapeutic (continued MALG therapy for early breakthrough rejection, n = 67 [15.6%], mean no. days of ALG = 17.2). The study groups were comparable and retrospectively analyzed in multivariate fashion for 15 variables. Requirement for postoperative dialysis was equivalent (14%) in both sequential and extended ALG groups. Extended ALG therapy failed to reduce the incidence of acute rejection (46.5% vs. 40.4% with true sequential therapy). Prolonging the duration of ALG treatment (greater than 10 days) was associated with a higher risk of infection. Logistic regression analysis revealed that the use of OKT3 after ALG accounted for the higher infection rate. Duration of ALG therapy had no impact on patient or graft survival after a mean follow-up interval of 20 months. We recommended a quadruple immunosuppressive strategy in cadaveric renal transplantation with sequential MALG/CsA to minimize early allograft dysfunction and to achieve excellent patient and graft survival. MALG therapy should be stopped after renal function is documented and CsA levels are therapeutic. Further ALG therapy offers no immunologic advantage and may place the patient at high risk for infection if OKT3 rescue therapy is required.