Definitions of acute rejection for clinical trial use would allow for standardized comparison of outcomes. The medical literature reporting trial results was searched to record definitions used in controlled trials. Over 6,000 refereed transplantation articles were searched for the following keywords: randomized controlled trials, multicenter studies, clinical trials, phase III, and immunosuppressive agents. Only three references resulted. Another pass through the literature resulted in 11 prospective studies on induction therapy and two prospective antirejection therapy studies that met the criteria for the search. Retrospective studies appearing in the literature search were two induction citations and seven antirejection therapy reports. Rejection criteria ranged from having been given no definition in both outcomes of induction trials as well as reports on antirejection therapy to having a large-scale list of criteria not all of which had to be met by every rejection case in a given study to be termed rejection. The transplant literature that was reviewed frequently provided only vague descriptions of the methodologies used to diagnose rejection and rejection reversal. The Efficacy Endpoints Conference on Kidney Transplant Rejection was formulated to review kidney transplant rejection using a database of consecutive rejection episodes. An attempt to derive definitions for clinical trial endpoints in kidney transplant rejections was planned for the conference because of a lack of continuity in the transplant literature.