Solid organ transplantation has rapidly developed into the therapy a choice for end-stage organ failure. The expansion of its use has resulted is a large deficiency in organ supply. To address this, the field of organ transplantation has attempted to develop new strategies that would increase the availability of organs for transplant. Some of these strategies include expansion of the donor pool by increasing the number of living donors or using deceased donor organs that may be marginal or "expanded". The intent is to bring life-saving therapy to individuals in need; however, much of this expansion has been brought forward without clear prospective guidelines. This article focuses on the current disparity between organ supply and demand, and how this has impacted the use of living donors and development of the "expanded donor" concept.