This study tested the proposal that negative appraisals represent a risk factor for developing posttraumatic stress disorder (PTSD) after trauma. Trainee firefighters (N = 68) were assessed during training (before trauma exposure) for PTSD, history of traumatic events, and tendency to engage in negative appraisals. Firefighters were reassessed 4 years later (N = 52), after commencing firefighter duty (after trauma exposure), for PTSD and depression using the Posttraumatic Stress Disorder Scale (E. B. Foa, L. Cashman, L. Jaycox, & K. Perry, 1997) and the Beck Depression Inventory (Version 2; A. T. Beck, R. A. Steer, & G. K. Brown, 1996). At follow-up, 12% met criteria for PTSD. Pretrauma negative appraisals about oneself accounted for 20% of variance in PTSD severity at follow-up. These data provide the first evidence that preexisting negative appraisals are a risk factor for PTSD.