Past research indicates that men are more physically aggressive than women, but very little research has examined mediators of this gender difference. Indeed, the only established finding to date is that one plausible mediator – namely trait anger – shows no reliable gender difference whatsoever. Drawing on sexual selection theory and social-learning theories, we predicted that revenge may mediate this gender difference even though anger does not. Three studies using both personality questionnaires (Studies 1 and 2) and objective laboratory measures of aggression (Study 3) provided support for this contention. The results provide some of the first evidence for a reliable mediator of gender difference in physical aggression.