The effect of traumatic events on memory has been, and continues to be, one of the most controversial areas in psychology. In this talk I will describe the contrasting effects on involuntary memory - vivid reliving in the present - and on voluntary memory - fragmentation and disorganisation. I will then discuss the issue of whether memories of trauma can be completely forgotten and later remembered from the perspectives of theory and evidence. The final topic will be our understanding of how the brain and body respond when traumatic moments are encoded.