Participants: One thousand forty-six adolescents and young adults aged 13 to 21 years completed a selfreport questionnaire. Main Exposures: War-related traumatic events, posttraumatic stress symptoms, and sociodemographic variables. Main Outcomes Measures: The Adolescent Complex Emergency Exposure Scale, specifically designed for this region, screened for exposure to potentially traumatic events, and the Impact of Event Scale-Revised measured symptoms of posttraumatic stress consistent with Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition) criteria. Results: Among the 477 girls (45.6%) and 569 boys (54.4%) in the study, 95.0% reported at least 1 traumatic event. On average, adolescents were exposed to 4.71 traumatic events, with higher exposure rates reported in boys, older groups, rural and urban areas, and respondents whose mother or father was dead. Of 990 respondents, 52.2% met symptom criteria for posttraumatic stress disorder. Symptom scores were strongly related to cumulative trauma exposure; however, the strength of this relationship differed slightly across living area groups for girls. Conclusion: Adolescents in the eastern Democratic Republic of Congo are highly exposed to political violence, putting them at a considerable risk-mediated by living area and sex-to develop posttraumatic stress symptoms.