To study differences in the effects of stress exposure and affective responding on aggression in men and women, the authors examined the effects of an acute stressor (air blast) on subsequent aggressive behavior, measured as the intensity of shocks men and women delivered to a putative employee. The authors measured participants' affective responding using the startle reflex. Results showed that although men and women did not differ in their startle responses to the actual stressor, high stress led to contrasting patterns of subsequent aggressive behavior. Women under high stress responded with less aggression than women under low stress, whereas men exposed to high stress exhibited increases in aggression relative to those under low stress. Affective responding during the stressor differentially modulated aggression in men and women: Startle responses predicted increasing levels of aggression in men and less aggression in women. These findings suggest that although men and women show similar basic affective processing in response to stressors, the behavioral profiles associated with stress differ in men and women. These findings have implications for understanding gender differences in the prevalence of internalizing and externalizing psychopathology.