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DOI:10.1097/MOT.0000000000000645 The remarkable progress in solid organ transplantation over the past half century has saved hundreds of thousands of lives worldwide, reversing heretofore fatal end-stage organ failure. However, from its inception, the limited supply of transplantable organs constrains access to beneficial transplant procedures leading to the need to implement systems to allocate available organs among waiting candidates. Defining equitable, efficient and transparent systems to assign organs is vital to maintain public trust in the organ transplant enterprise and preserve our current system of voluntary organ donation. Recovery of deceased donor organs also challenged medical professionals to define an ethically acceptable framework within which the greatest number lifesaving organs can be recovered and transplanted. In 1968, the Ad Hoc Committee of the Harvard Medical School to Examine the Definition of Brain Death published a definition of ‘Irreversible coma’ [1]. Once adopted into legislative language in the United States and many other nations, the concept of brain death allowed the legal recovery of organs from heart beating donors. Over the ensuing decades, there has been slow progress in expanding the organ supply by maximizing the number of organs that can be transplanted from each gift and considering donors that were previously deemed unacceptable (e.g. HIV-infected organs and elderly donors) [2,3]. However, this progress is insufficient to meet the growth in demand for organ transplantation. This issue of the journal addresses two of the principle challenges facing organ transplantation in the next decade: ensuring an ethical and efficient organ allocation system and expanding the supply of potentially transplantable organs. The assessment of any organ allocation system is complex given the competing priorities facing transplant leaders. In his contribution, Dr Schold has described a series of important metrics that should be considered in assessing organ allocation systems including effectiveness (the health benefits derived from the recovered donor organs); equity (ensuring parity in access to organ transplant for patients with similar medical conditions); efficiency (the cost and