Abstract: In September 2012, the government-chartered body responsible for allocating cadaveric organs in the United States proposed a plan to make better use of the scarce supply of kidneys through "longevity matching." Critics have charged the plan with age discrimination, since it will deliberately allocate high-quality kidneys to younger candidates at the expense of older candidates with equal or greater medical need. These allegations raise significant legal and moral questions, and the debate they have sparked offers a revealing vantage point on the ways discrimination is conceptualized within and outside the law. This paper offers the first analysis of the legality of the proposal under the Age Discrimination Act of 1975, which bars age discrimination in federally funded programs. It then argues that the statute fails to speak to the central moral concerns about the plan, which have less to do with instrumental irrationality or arbitrariness than with the potential for discriminatory rationing to denigrate the equal worth of older people.