If self-regulation is a limited resource, the capacity to inhibit aggressive behavior should be lower among people who have already exercised self-regulation. In Experiment 1, participants who had to resist the urge to eat tempting food later reacted more aggressively to an insult than other participants who were allowed to eat as much as they wanted. In Experiments 2 and 3, some participants had to self-regulate by making themselves concentrate on a boring film and stifling their physical and facial movements, and afterward they, too, responded more aggressively than controls. Experiment 3 also showed that the results were not due to differential moods and that one act of self-regulation (unrelated to aggression) was sufficient to enhance subsequent aggressive responses toward the experimenter. Copyright © 2006 John Wiley & Sons, Ltd.