In this paper, I argue for the following points. First, all of us have a presumptive moral obligation to be organ donors if we are in the relevant medical circumstances at the time of death. Second, family members should not have the right to interfere with the fulfillment of that obligation. Third, the ethical basis for that obligation is reciprocity. If we want a sufficient number of organs available for transplantation, then all must be willing donors. Fourth, that likelihood is diminished if individuals are entirely free to refuse to be organ donors but still would demand to be organ recipients. Fifth, although individuals would be ethically obligated to be organ donors, we still need to permit them to refuse to be organ donors. Sixth, to encourage individuals to stay within the organ donation system, we should have as a just and ethically justified policy denying individuals an organ transplant in the relevant medical circumstances if they have chosen to exit the organ donation system. Individuals would not be permitted to be organ recipients if they were unwilling to be organ donors. This is what it means to be part of what Rawls in Political liberalism (15-22) would refer to as a “fair system of social cooperation.” We refer to this as the “reciprocity requirement.”