After Kravinsky learned that many African-Americans have difficulty obtaining kidneys from family members, he sought out a hospital in Philadelphia that would allow him to donate one of his kidneys to a lower-income black person.
According to Peter Singer, writing in The New York Times, Kravinsky justified the donation mathematically when speaking to Singer's students, noting that the chances of dying as a result of the procedure would have been about 1 in 4,000. Kravinsky believed that, under the circumstances, "to withhold a kidney from someone who would otherwise die means valuing one’s own life at 4,000 times that of a stranger", a ratio he termed "obscene."
Following the kidney donation, Kravinsky did several interviews with the media, including a radio conference with Robert Siegel of NPR and a TV appearance on CBS among others. During some of these public interviews, Kravinsky argued that should someone be, for instance, on the verge of curing cancer but would die unless Kravinsky were to donate his second kidney, that being the only match in the world, that it would be morally correct to donate the kidney in order that millions of people would be saved. Kravinsky has noted that this admittedly theoretical and highly improbable scenario is the logical extension of someone risking his life by jumping into icy water to save a child, or a soldier cradling a hand grenade to save his buddies.