Freud proposed that unwanted memories can be forgotten by pushing them into the unconscious, a process called repression(1). The existence of repression has remained controversial for more than a century, in part because of its strong coupling with trauma, and the ethical and practical difficulties of studying such processes in controlled experiments. However, behavioural and neurobiological research on memory and attention shows that people have executive control processes directed at minimizing perceptual distraction(2,3), overcoming interference during short and long-term memory tasks(3-7) and stopping strong habitual responses to stimuli(8-13). Here we show that these mechanisms can be recruited to prevent unwanted declarative memories from entering awareness, and that this cognitive act has enduring consequences for the rejected memories. When people encounter cues that remind them of an unwanted memory and they consistently try to prevent awareness of it, the later recall of the rejected memory becomes more difficult. The forgetting increases with the number of times the memory is avoided, resists incentives for accurate recall and is caused by processes that suppress the memory itself. These results show that executive control processes not uniquely tied to trauma may provide a viable model for repression.