After 15 years of sustained research efforts, a new humanized monoclonal antibody, daclizumab (Zenapax®), has become available for use in preventing acute rejection following renal transplantation. Two large, double-blind, placebo-controlled multicenter trials in the U.S. and Europe have shown that acute rejection episodes were reduced by 35-43% in those receiving daclizumab along with cyclosporine and corticosteroids (as well as azathioprine in the U.S. study). In a third blinded trial, 75 renal transplant patients received either daclizumab or placebo in combination with cyclosporine, mycophenolate mofetil and corticosteroids. Only 12% of the daclizumab group experienced acute rejection during the first 6 months after transplantation vs. 20% in the control patients, with no difference in infectious complications. Daclizumab is a novel, revolutionary therapy in transplantation; unlike other agents, it has improved outcomes without introducing new a lverse effects.