An examination of the ethical issues raised by the possibility of human life extension, including its desirability, unequal access, and the threat of overpopulation. Life extension—slowing or halting human aging—is now being taken seriously by many scientists. Although no techniques to slow human aging yet exist, researchers have successfully slowed aging in yeast, mice, and fruit flies, and have determined that humans share aging-related genes with these species. In New Methuselahs, John Davis offers a philosophical discussion of the ethical issues raised by the possibility of human life extension. Why consider these issues now, before human life extension is a reality? Davis points out that, even today, we are making policy and funding decisions about human life extension research that have ethical implications. With New Methuselahs, he provides a comprehensive guide to these issues, offering policy recommendations and a qualified defense of life extension. After an overview of the ethics and science of life extension, Davis considers such issues as the desirability of extended life; whether refusing extended life is a form of suicide; the Malthusian threat of overpopulation; equal access to life extension; and life extension and the right against harm. In the end, Davis sides neither with those who argue that there are no moral objections to life enhancement nor with those who argue that the moral objections are so strong that we should never develop it. Davis argues that life extension is, on balance, a good thing and that we should fund life extension research aggressively, and he proposes a feasible and just policy for preventing an overpopulation crisis.