BACKGROUND: Daclizumab (Zenapax, Roche Pharmaceuticals), a humanized monoclonal antibody directed against the alpha chain of the interleukin 2 receptor, has been shown to reduce the incidence of acute rejection at 6 months after renal transplantation in two phase III clinical trials. This report presents the combined 1- and 3-year outcomes of kidney transplant recipients who participated in these two phase III clinical trials. METHODS: Data from two multicenter, randomized, placebo-controlled trials were evaluated with regard to graft survival, patient survival, incidence of malignancies (including lymphoma), renal function (serum creatinine and glomerular filtration rate [GFR]), and current maintenance immunosuppressive regimen. In addition, the impact of acute rejection and acute rejection requiring treatment with antilymphocyte therapy upon 3-year graft survival was evaluated. Daclizumab was compared to placebo on a background of cyclosporine (CsA), azathioprine, and corticosteroids (triple therapy, TT) or CsA and corticosteroids (double therapy, DT). RESULTS: Treatment with daclizumab in the pooled analysis demonstrated a significant reduction in the incidence of biopsy-proven acute rejection episodes at 12 months posttransplant (43% vs. 28%, P