Kidney paired donation (KPD) was first suggested in 1986, but it was not until 2000 when the first paired donation transplant was performed in the USA. In the past decade, KPD has become the fastest growing source of transplantable kidneys, overcoming the barrier faced by living donors deemed incompatible with their intended recipients. This review provides a basic overview of the concepts and challenges faced by KPD as we prepare for a national pilot program with the United Network for Organ Sharing. Several different algorithms have been creatively implemented in the USA and elsewhere to transplant paired donors, each method uniquely contributing to the success of KPD. As the paired donor pool grows, the problem of determining allocation strategies that maximize equity and utility will become increasingly important as the transplant community seeks to balance quality and quantity in choosing the best matches. Financing for paired donation is a major issue, as philanthropy alone cannot support the emerging national system. We also discuss the advent of altruistic or non-directed donors in KPD, and the important role of chains in addition to exchanges. This review is designed to provide insight into the challenges that face the emerging national KPD system in the USA, now 5 years into its development.