Abstract Intrusive imagery is both a common response to trauma and a hallmark of Posttraumatic Stress Disorder. However, its features and underlying mechanisms have not been reviewed systematically. This paper delineates the characteristics of intrusions and critically reviews the literature, conceptualizing intrusive imagery as an emotional memory phenomenon. This approach integrates otherwise separate research arenas in emotion and memory, psychobiology, pharmacology, and physiology, which converge to suggest that intrusive imagery is driven primarily by affective arousal and sympathetic nervous system reactivity. These basic and applied research findings are addressed directly by three information processing theories, which are reviewed and critiqued for their heuristic value in accounting for intrusions. Directions for research, treatment, and assessment are presented.