A randomized and controlled study was conducted to evaluate the efficacy of adjunctive antithymocyte globulin (ATG) therapy for the treatment of the initial rejection episode in first cadaveric transplants. When compared to the control group (29), which received only standard antirejection treatment (SAT) of steroid pulsing and local irradiation, the adjunctive ATG treatment group (23) demonstrated significantly faster recovery rates (8.9 +/- 4.1 versus 6.9 +/- 3.7 days, P = 0.05, respectively) and better graft survival rates (62 +/- 9% versus 91 +/- 7%, respectively) after the first rejection. ATG treatment did not result in fewer subsequent rejection episodes than SAT but long-term allograft survival rates remained superior to controls for the entire 3-year study period. By avoiding ATG treatment in those patients who never experienced clinical rejection on maintenance immunosuppressive therapy, i.e., nonresponders (23 of 90), complications associated with excessive immunosuppression were minimized. The combined results of the non-responder group of patients and ATG-treated patients resulted in a 1-year patient survival of 97% and graft survival of 86%. These results suggest that the most efficacious use of ATG is therapeutic and not prophylactic in renal transplant patients.