SOME PERSONS who experience psychic trauma report that memories of the precipitating event intrusively enter their awareness long after the traumatic event takes place. Such clinical observations have led to the theory that there is a compulsion to re-enact traumas, perhaps as a belated attempt at mastery. This paper reports an experimental study of this theory in which a stressful film induced subsequent unbidden images in volunteer subjects. The Repetition of Psychic Trauma.—Freud and Breuer1described psychic trauma as an event in which perceptual and affective stimuli overwhelm the processes that ordinarily bind them and maintain homeostasis. These stimuli tend to return to mind, sometimes as visual images. In the "Project for a Scientific Psychology,''2Freud calls such vivid images ``untamed memories." When affects associated with the trauma are worked through, the memories become "tamed"; that is, reduced in intensity and sensory quality. But, if conflict interferes