This protocol will test a novel dual agent combination therapy for its ability to prevent human renal allograft rejection. Thymoglobulin (Sangstat), a FDA-approved polyclonal rabbit-IgG antithymocyte preparation, will be given for ten days at the time of transplantation to achieve profound lymphocyte depletion. This will be paired with chronic therapy with Sirolimus (rapamycin, Wyeth-Ayerst), an oral immunosuppressant agent recently approved by the FDA. Rapamycin allows for antigen specific T cell activation but prevents T cell clonal expansion by interrupting IL-2 receptor beta-chain signal transduction. The rationale for this combination is to eliminate existing alloreactive T cell clones that could initiate a rejection at the time of transplantation, and to promote graft specific activation induced cell death (AICD) in repopulating T cells such that an allospecific T cell deficit is induced. The desired effect of this therapy is to prevent allograft rejection without the chronic use of calcineurin inhibitors or glucocorticosteroids, and in doing so, develop a regimen for transplantation that avoids most of the chronic drug toxicities inherent in the use of these two classes of immunosuppressants.