An apology is a strong and cheap device to restore social or economic relationships that have been disturbed. In a laboratory experiment we find that harmdoers use apologies in particular if they fear punishment and when their intentions cannot be easily inferred. After offenses with ambiguous intentionality apologizers are punished less often than nonapologizers. Victims expect an apology and punish if they do not receive one. If an apology is possible, harmdoers who apologize are punished with lower probability. An apology only affects the event of punishment but not the level of punishment. An apology does not help at all after clearly intentionally committed offenses. On the contrary, after such offenses harmdoers do better not to apologize since sending an apology in this situation strongly increases punishment compared to remaining silent.
