A potentially traumatic event (PTE) contributes to trauma through its frequency, conditional probability of posttraumatic stress disorder (PTSD), and experience of other PTEs. A cross-sectional survey was conducted, enrolling 21,425 adults nationally representative of six European countries. Using the WHO-Composite International Diagnostic Interview, 8,797 were interviewed on 28 PTEs and PTSD. Prevalence of 12-month PTSD was 1.1%. When PTSD was present, the mean number of PTEs experienced was 3.2. In a multivariate analysis on PTEs and gender, six PTEs were found to be more traumatic, and to explain a large percentage of PTSD, as estimated by their attributable risk of PTSD: rape, undisclosed private event, having a child with serious illness, beaten by partner, stalked, beaten by caregiver.