Research on terror management theory has found evidence that people under mortality salience strive to live up to salient cultural norms and values, such as egalitarianism, pacifism, or helpfulness. A basic and strong internalized norm in most human societies is the norm of reciprocity: People should support those who have supported them, and people should injure those who have injured them, respectively. In two experiments, the authors demonstrate that mortality salience increases adherence to the norm of reciprocity. In Study 1, a favor of a server led to higher tipping after making mortality salient. Study 2 indicated that mortality salience motivated participants to act according to their high dispositional relevance of the norm of negative reciprocity following an unfavorable treatment: Those participants gave less money to a person who had previously refused to help them.