Individual differences are thought to influence the propensity for exposure to trauma and the subsequent development of post-traumatic stress disorder (PTSD) symptoms. Prior research has identified pre-existing mood disorders as one such individual risk factor for traumatic events as well as for PTSD. The present study reports the incidence of traumatic events (and PTSD) and examines psychiatric risk factors for trauma exposure in a prospective community sample. Data come from a prospective, longitudinal epidemiological study of adolescents and young adults (age 14-24) in Munich, Germany. Respondent diagnoses (N = 2,548) at baseline and at follow-up 34-50 months later were considered. Psychiatric diagnoses at baseline were examined as predictors of qualifying trauma. Baseline prevalence of persons having experienced trauma meeting DSM-IV A1 and A2 criteria ('qualifying trauma') was 16.7%; during the follow-up period, 20.3% persons had experienced incident (new) qualifying traumata. The prevalence of PTSD, including subthreshold cases, at baseline was 5.6%; by the end of the follow-up period this had increased to 10.3%. Presence of an anxiety disorder at baseline predicted exposure to qualifying traumas during the follow-up period (adjusted ORs ranging from 1.36 for any trauma type to 3.00 for sexual trauma); this association was apparently due to an increased tendency to report events as being particularly horrific (meeting A2 criteria). In contrast, presence of illicit drug use predicted the onset of traumatic events (specifically assaultive and sexual trauma) meeting at least A1 criteria, suggesting an actual exposure to these types of traumatic events for this class of disorders. In this prospective study of urban adolescents and young adults, certain classes of pre-existing psychiatric disorders (most notably anxiety disorders and illicit drug use disorders) were associated with increased risk for qualifying traumatic events. The mechanisms by which premorbid psychiatric disorders promote exposure to traumatic events are unknown. Better understanding of these pathways may lead to novel strategies for primary and secondary prevention of PTSD.