Journal of Social and Clinical Psychology 30(6): 549-569 Trait negative emotion has been identified as a potential moderator of the effect of expressive writing on symptoms of posttraumatic stress. The goal of this study was to investigate whether individuals who differed in degree of trait negative emotion (high vs. low) responded differently to three different writing tasks. These tasks included an expressive writing condition in which participants wrote about a traumatic event, an active control condition in which participants wrote about a traumatic event in a nonemotional manner, and a control condition in which participants wrote about daily activities. One hundred twenty undergraduates completed one of these writing tasks for 30 minutes on two consecutive days. Results revealed that participants high in trait negative emotion endorsed significantly greater symptoms of posttraumatic stress and emotional arousal than participants low in trait negative emotion, regardless of writing condition. Results further showed a significant reduction in posttraumatic stress symptoms among high trait negative emotion individuals assigned to the expressive writing condition but no significant reduction in other conditions. Participants high in trait negative emotion also rated the writing task as significantly more difficult and distressing than participants low in trait negative emotion; nonetheless, both groups indicated that the task was equally helpful.