Objectives. This study aimed to examine the structure of self-reported post-traumatic stress disorder (PTSD) symptoms. Design. Based on previous factor analytic findings and the DSM-IV formulation, six confirmatory factor models were specified and estimated that reflected different symptom clusters. Methods. The analyses were based on responses from 1116 participants who had suffered whiplash injuries and screened for full or subclinical PTSD using the Harvard Trauma Questionnaire. Results. A correlated four-factor model with re-experiencing, avoidance, dysphoria and arousal factors fitted the data very well. Correlations with criteria measures showed that these factors were associated with other trauma related variables in a theoretically predictable way and showed evidence of unique predictive utility. Conclusions. These results concur with previous research findings using different trauma populations but do not reflect the current DSM-IV symptom groupings.