The therapy-enhancement distinction occupies a central place in contemporary discussions of human genetics and has been the subject of much debate. At a recent conference on gene therapy policy, scientists predicted that within a few years researchers will develop techniques that can be used to enhance human traits. In thinking about the morality of genetic interventions, many writers have defended somatic gene therapy, and some have defended germline gene therapy, but only a handful of writers defend genetic enhancement, or even give it a fair hearing. The mere mention of genetic enhancement makes many people cringe and brings to mind the Nazi eugenics programs, Aldous Huxley's Brave New World, “The X-Files,” or the recent movie “Gattaca.” Although many people believe that gene therapy has morally legitimate medical uses, others regard genetic enhancement as morally problematic or decidedly evil.