While epidemiological studies have shown that women have a greater tendency than men to develop posttraumatic stress disorder (PTSD) following traumatic events, the reasons for this difference are not clearly understood. Despite increasing interest in neurobiological factors in PTSD (including sustained amygdala and skin conductance responses to fear-provoking stimuli), sex differences in neural activations to threat have received little investigation. A study published in a recent issue of the Journal of Abnormal Psychology tested the prediction that trauma would heighten activity in automatic fear-processing networks to a greater extent in women than in men. Functional magnetic resonance imaging (fMRI) data were recorded in 23 participants with PTSD (13 women, 10 men) , 21 trauma-exposed controls (9 women, 12 men) , and 42 non-trauma-exposed controls (22 women, 20 men) while they viewed masked facial expressions of fear. Exposure to trauma was associated with enhanced brainstem activity to fear in women, regardless of the presence of PTSD, but in men, it was associated only with the development of PTSD. Men with PTSD displayed greater hippocampal activity to fear than did women. Both men and women with PTSD showed enhanced amygdala activity to fear relative to controls. Age, depression, and anxiety were ruled out as confounding variables. The authors concluded that greater brainstem activation to threat stimuli may contribute to the greater prevalence of PTSD in women, and greater hippocampal activation in men may be linked to an enhanced capacity for evaluating fear-related stimuli.