To examine the lifetime prevalence of trauma experiences and post-traumatic stress disorder (PTSD). Questionnaire-assessed PTSD, the type of traumatic event experienced, perceived trauma impact, and trauma frequency in 1824 randomly selected men and women. PTSD lifetime prevalence was estimated at 5.6% with a 1 : 2 male-to-female ratio, in spite of men reporting greater trauma exposure. The highest PTSD risk was associated with sexual and physical assault, robbery and multiple trauma experiences. Controlling for trauma type did not account for gender differences, while controlling for experienced distress did. The conditional probability for PTSD varied as a function of trauma type, frequency and impact of the event, with increased rates associated with prevalent trauma exposure and higher perceived distress. The latter accounted for the gender effect, suggesting that gender differences in PTSD in part represent a generally greater vulnerability to stress in women.