Entrepreneurs have been very much present throughout the history of organ transplantation. This is partly due to the well-known failure of the supply of organs to meet demand for them, a circumstance that generally produces pressure for some sort of creative response. But our interest in the case goes beyond this. The history of innovation in organ transplantation is, of course, partly one of medical advances and technical developments that have made it possible—even routine—to safely remove a kidney from one person and put it in someone else. But it has also been a history of active exploration, innovation, and management of a potentially very controversial exchange at the seemingly clear boundaries that separate giving from selling, life from death, and right from wrong. Traffic across these boundaries, and experimentation with its form and scope, has been a feature of organ exchange since its earliest days. It has partly been a cultural process, with transplant innovators actively exploring what people will or will not tolerate when it comes to transferring goods or providing services under potentially controversial circumstances. It has partly been an organizational problem, as participants experimented with the logistical infrastructure necessary to accomplish the needed exchanges in some desired form. And it has also presented a legal challenge, as the entrepreneurs developing methods and rules of exchange have carried out their innovations in the shadow of the law. This has meant managing constraints or avoiding penalties imposed by legal requirements, and navigating legal obstacles that have sometimes proved to be real, and sometimes imagined.