It is argued here that bioethicists might inadvertently be promoting genetic determinism: the idea that genes alone determine human traits and behaviours. Discussions about genetic testing are used to exemplify how they might be doing so. Quite often bioethicists use clinical cases to support particular moral obligations or rights as if these cases were representative of the kind of information we can acquire about human diseases through genetic testing, when they are not. On other occasions, the clinical cases are presented in simplistic ways that portray genetic testing as yielding information more accurate than it actually is. It is concluded that, because of the problematic implications that the ideology of genetic determinism might have for individuals' wellbeing and for our public policies, bioethicists should be careful to present these issues in ways that do not promote questionable ideas about the causal role of genes in human diseases and behaviours.