The number of kidneys transplanted to people over age 70, both from living and cadaver donors, has increased steadily in the past two decades in the United States. Live kidney donation, on the rise for all age groups, opens up new dimensions of intergenerational relationship and medical responsibility when the transfer of organs is from younger to older people. There is little public knowledge or discussion of this phenomenon, in which the site of ethical judgment and activism about longevity and mortality is one's regard for the body of another and the substance of the body itself is ground for moral consideration about how kinship is "done." The clinic, patient, and patient's family together shape a bond between biological identity and human worth, a demand for an old age marked by somatic pliability and renewability, and a claim of responsibility that merges the "right to live" and "making live." Live kidney transplantation joins genetic, reproductive, and pharmacological forms of social participation as one more technique linking ethics to intervention and the understanding of the arc of human life to clinical opportunity and consumption. Significant in this example is the medicocultural scripting of transplant choice that becomes a high-stakes obligation in which the long-term impacts on generational relations cannot be foreseen.