Abstract: BACKGROUND: Accumulating data suggest that the structure of posttraumatic stress disorder (PTSD) symptoms may be more nuanced than proposed by prevailing nosological models. Emerging theory further suggests that an 8-factor model with separate internally- (e.g., flashbacks) and externally- (e.g., trauma cue-related emotional reactivity) generated intrusive symptoms may best represent PTSD symptoms. To date, however, scarce research has evaluated the fit of this model and whether index traumas are differentially associated with it in populations at high risk for trauma exposure, such as military veterans. METHODS: Data were analyzed from a nationally representative sample of 3847 trauma-exposed U.S. veterans who participated in the National Health and Resilience in Veterans Study. Confirmatory factor analyses were conducted to evaluate the fit of a novel 8-factor model of PTSD symptoms relative to 4-factor DSM-5 and empirically-supported 7-factor hybrid models. RESULTS: The 8-factor model fit the data significantly better than the 7-factor hybrid and 4-factor DSM-5 models. Combat exposure and harming others were more strongly associated with internally-generated intrusions, while interpersonal violence and disaster/accident showed stronger significant associations with externally-generated intrusions. LIMITATIONS: The 8-factor model requires validation in non-veteran and more diverse trauma-exposed populations, as well as with clinician-administered interviews. CONCLUSIONS: Results of this study provide support for a novel 8-factor model of PTSD symptoms that is characterized by separate internally- and externally-generated intrusions. They also suggest that certain index traumas may lead to differential expression of these symptoms.