The present study evaluated the relative importance of different cognitivefactors (anxiety sensitivity and trauma-related beliefs) in predicting PTSDsymptom severity and treatment-related changes in these symptoms. Eighty-onevictims of motor vehicle accidents (MVAs) completed self-report measures ofPTSD symptoms, anxiety sensitivity (AS), MVA-related beliefs and controlvariables (e.g., medication use, pain severity). A subsample of patients(n=28), who received cognitive-behavioural treatment for PTSD, completedthese measures pre- and post-treatment. For the combined sample (n=81),regression analyses indicated that AS and pain severity were significantpredictors of PTSD symptoms, whereas MVA-related beliefs were not. Forpatients completing treatment, regression analyses indicated thatreductions in AS and pain severity were significant predictors ofreductions in PTSD symptoms. MVA-related beliefs did not significantlypredict symptom reduction once AS, pain severity and medication statuswas controlled for. These findings suggest that AS is a significantcognitive risk factor for exacerbating and maintaining PTSDsymptoms. Treatment implications are discussed.