The study examined the relationship of extraversion, neuroticism, and impulsiveness with posttraumatic stress reactions of avoidance and intrusion. 36 outpatients from a trauma unit at a major metropolitan hospital in Melbourne (Victoria), and 24 age-matched controls completed the Impact of Event Scale, the Eysenck Personality Questionnaire Revised, and the Impulsivity Questionnaire. Intrusion symptoms were predicted both by Extraversion and Neuroticism, after controlling for age and gender, with Neuroticism making a stronger contribution to the prediction. The only predictor of Avoidance symptoms was Neuroticism. Impulsivity correlated with Intrusion symptoms but predicted them only in the trauma group. This finding, along with the observed positive associations of Extroversion with both posttraumatic symptoms, lends support to Gray's model of dispositions influencing responses to trauma, suggesting that impulsive (extroverted) neurotics are more vulnerable to posttraumatic stress than introverted ones.