Previous research on vulnerability to Post-Traumatic Stress Disorder (PTSD)has been restricted by the absence of prospective studies that measureindividual differences prior to traumatization. This study investigatedthe predictors of analogue post-traumatic intrusive cognitions using afully prospective design. Non-patient participants completed a range ofpredictor measures before being exposed to a film about a traumaticfire. Film-induced changes in negative mood were also assessed. Subsequentintrusions were measured both within the experimental session and for afurther seven days. The hypothesized predictors were: neuroticism, traitanxiety, extraversion, depression, a general tendency to suppress unpleasantthoughts, beliefs about being “at risk” from fire, mentalimagery, self-rated proneness to intrusions and negative mood changes. Theresults showed that intrusions were predicted by film-induced increases innegative mood, thought suppression tendencies, beliefs about vulnerabilityto fire and self-rated proneness to intrusive cognitions. The findings arediscussed in relation to the literature on thought suppression andcognitive processes in PTSD.