This article challenges recent calls for moral bioenhancement-the use of biomedical means, including pharmacological and genetic methods, to increase the moral value of our actions or characters. It responds to those who take a practical interest in moral bioenhancement. I argue that moral bioenhancement is unlikely to be a good response to the extinction threats of climate change and weapons of mass destruction. Rather than alleviating those problems, it is likely to aggravate them. We should expect biomedical means to generate piecemeal enhancements of human morality. These predictably strengthen some contributors to moral judgment while leaving others comparatively unaffected. This unbalanced enhancement differs from the manner of improvement that typically results from sustained reflection. It is likely to make its subjects worse rather than better at moral reasoning.