Many people believe that a person’s sexual orientation is genetic. Given the widespread prejudice against, and hatred of, lesbians, gay men, and bisexuals in many societies, it seems likely that many parents will be interested in using genetic technologies to prevent the birth of children who will not be heterosexual. This paper considers the moral and legal implications of such procedures, whether or not they would work. It is argued that the availability of procedures to select the sexual orientation of children would contribute to discrimination and prejudice against lesbians, gay men and bisexuals and, more generally, undermine the maintenance of a just society. These effects carry significant weight in determining whether genetic technologies should be developed and whether their use is, or should be, legally permissible and morally acceptable.