Herein are presented the results of a controlled prospective randomized double-blind evaluation of antilymphoblast globulin as an immunosuppressive adjunct to azathioprine and prednisone in cadaver renal transplantation. There were 31 patients and 36 patients randomly assigned to therapeutic and control groups, respectively. ALG-treated patients experienced no major side-effects, a delayed onset of rejection following transplantation (P less than .005), a reduced total number of rejection episodes (P less than .05), fewer days in the hospital (P less than .05), a reduced cost of transplantation (P less than .02), improved graft survival (P less than .05), and patient survival equivalent to that of the control group. These data indicate that ALG is safe, cost-effective, and of immunologic benefit in cadaver renal transplantation.