Killing someone in order to save several lives seems more morally acceptable to men than to women. We suggest that this greater approbation of utilitarian killings may reflect gender differences in the tolerance to inflicting physical harm, which are partly the product of sexual selection. Based on this account, we predicted that men may be less utilitarian than women in other conditions. In four studies, we show that men are more likely than women to make the anti-utilitarian (hypothetical) choice of causing three same sex deaths to save one opposite sex life; and that this choice is more likely when there are fewer potential sexual partners, more likely for heterosexual men and less likely if the female character to be saved no longer has reproductive value.