Many important advances in transplantation have been made during the last decade. The introduction of Orthoclone OKT3 into clinical trials and its subsequent approval by the Food and Drug Administration in 1985 for use as an antirejection agent for renal transplantation were landmarks in the field of clinical transplantation of solid organs. In the decade since the approval of OKT3 for clinical use, much has been learned and written about OKT3. OKT3 now is considered a safe and effective agent for prophylaxis and first-line treatment of acute rejection of solid organ allografts. In this article, the development and use of OKT3 over the last 10 years, as well as the present status and future implications of immune therapy with OKT3, are reviewed.